Think I Messed Up Bad - Deleted A Key in RegEdit I Shouldn't Have.

AlexM13 · 08 Jul 2017

So, I'm not gonna lie, I'm a geek and I just done goofed bad.

I was trying to fix an irritating problem - I accidentally set a file to "always open" .dat files and .pak files (I was using a tool to extract certain files from generic data files). I also did it with .exe because I was trying to look into something with an exe too.

Overall, I was just annoyed that this icon shows up for dat and pak files when they're just generic files and it shouldn't. But you can't just go into Default Programs and set it to "nothing" - if you don't have a program to fall back on, it's locked.

So I go a bit nuclear here and go into RegEdit and go and delete the keys for exe, dat, and pak entirely.

Yeahhh... I didn't know what it would do and it seems it wasn't terribly smart.

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Now I can't open ANY exes. Further, no files AT ALL can be opened because all files are associated to an exe program to open them. For example - can't open .txt files because .txt needs to be opened by notepad.exe... which Windows doesn't know how to open anymore.

I can't run CMD.

I can't run Windows Powershell.

I can't run regedit.

I can't open anything using Run.

I can't open Task Manager.

I bet if you sent me the reg files to fix it, it wouldn't be able to because it'd need to talk to RegEdit to work.

So... pretty bad error I've made here.

I know better than to reboot the system - I figure that may just lock me out of the system for good. I can still use Windows Explorer for now, but I figure that's just because I haven't closed it since I changed the registry key.

I've already begun the process of backing up all files on the system I really wanna keep - Documents, Downloads, Music, Pictures, and Videos, and I've got my other USB for booting from USB and format/reinstall Windows all over again ready, in case this is really a system-breaking mistake I've made.

... least it'll fix the registry issue I had. Kinda funny it went this far over something so small though.

This leaves me with a curious question... I thought exes are their own thing? Why does Windows think it needs something to open it? Is there something in Windows that typically handles exes? Perhaps I could fix this simply by changing the default program to the system file that's meant to handle it. I dunno, this is something I don't know about and could be something to learn - what actually handles exes. I thought they were just binary blobs that just run themselves.

Perhaps I've confused Windows to think there's supposed to be a default program for a type of file that there shouldn't be any default program for. I dunno.

Does anyone by chance know how to fix this without reinstalling Windows?

I figure this may be something a reboot might fix when Windows is trying to boot and it realizes something is amiss, but I don't wanna take that risk - for now I'm leaving it on so that I at least have access to file explorer. Keep in mind though.. no programs can be launched, not even system ones.

Thanks.

dencal · 08 Jul 2017

Holding down shift key while clicking on Restart should bring up Recovery Options.

AlexM13 · 08 Jul 2017

Yeah I kow that, but I figured that'll pull me out of explorer which could make matters worse. Further, I might be boned anyway because I don't think there's any restore points or backups for it to fall back on anyway.

And aside from that, isn't system restore stored in an exe as well? Or is that something that's loaded into memory anytime you open Windows?

I figure the only things Windows will be able to open right now are things that it opens/runs before it starts considering default programs and stuff. The pilot processes that get Windows open might still work I suppose, but I figure anything after the registry is all loaded up and everything won't work anymore. Not sure if even safe mode will help me now.

Not gonna do anything that would require a reboot yet until I get more input though reassuring that it'll be okay.

Crazy that one key change can mess up a computer so bad, huh? If everything kinda hinges on it like this. The system's ability to open exes is probably one of those most basic things for the computer.

cyberrufus · 08 Jul 2017

Restore Default File Type Associations in Windows 10 Windows 10 Customization Tutorials

AlexM13 · 08 Jul 2017

cyberrufus said:

Restore Default File Type Associations in Windows 10 Windows 10 Customization Tutorials

You're misunderstanding my problem. Read my whole post. This is not a typical file association issue.

Pressing the "Reset" button doesn't fix this. I'm suprised that the settings app will even open, it must be loaded into memory already as part of explorer or something. Stuff like control panel and settings are still accessible, while all the other things I listed, like CMD, are now inaccessible.

But yeah, this isn't as simple as pressing the "Reset" button in the File Associations. That doesn't fix exe. I figure this is a very strange issue that the reset tool wasn't designed to consider.

cyberrufus · 08 Jul 2017

System restore should take care of the problem.

AlexM13 · 08 Jul 2017

I'll try it then. Just didn't wanna leave explorer and get locked out.

System restore has no restore points. If it comes down to having to totally reinstall Windows I'll just do it from USB.

AlexM13 · 08 Jul 2017

Lol I've tried running it in Safe Mode and got the following error upon Windows opening:

"you'll need a new app to open this program - ms-get-started".

Man I really messed it up. I'm incredibly lucky Windows still opens at all. But yeah, Safe Mode is goofed too.

Also there's no meaningful restore points either. If there's no way to manually fix the registry I think I'll have to just reinstall Windows from USB.

If I could just access regedit and be told the defaults for exe I could probably fix this just by reversing what I did manually, but the issue is that I can't even run regedit. Such a mess.

Bree · 08 Jul 2017

AlexM13 said:

If there's no way to manually fix the registry I think I'll have to just reinstall Windows from USB.

Before you give up and do a clean install, try an in-place repair upgrade. This will allow you to keep your installed apps.

Repair Install Windows 10 with an In-place Upgrade

AlexM13 · 08 Jul 2017

Bree said:

Before you give up and do a clean install, try an in-place repair upgrade. This will allow you to keep your installed apps.

Repair Install Windows 10 with an In-place Upgrade

Well truthfully I've been considering doing a clean install anyway. The programs don't matter and can be reinstalled easily. I have their setup files all on one of my USBs after all.

Before this even happened I was already considering doing a clean install because I recently was trying to edit some video and audio files and was doing a frenzy of installing codecs and tools I'm not familiar with to do that. I've uninstalled them all... but from a security standpoint, it still makes me uneasy. I introduced a bunch of software I don't know anything about to it and even though I uninstalled them now, things could've been left behind. So I've been considering a clean install anyway to nuke it and start over.

I was asking more out of curiosity about this. It touches on more fundamental things, which are deep things that even your average geekier guy like me doesn't know -- How does Windows handle exes and binaries? What does Windows actually do when you "run" an executable?

Lately I've also been using tools to change memory values while a program is still loaded up. CheatEngine is aimed at games but you can do a ton of other things with it too, forcing things to bend to your will by directly accessing memory. I've been getting into hex-editor tools again and stuff again too, modifying values in exes and stuff.

What I was doing before with generic data files seemed to also kinda start touching on this kind of thing. The tool I was using was extracting other file from a generic data file - I believe it did so by identifying headers and footers inside the file.

I think the kinda topics I'm curious to know are things like how data is stored, how the system knows what a "file" is and where that "file" begins and ends on the hard drive platter, exactly what happens at the hardware level when you press that power button, how operating systems boot-up and the pilot processes that handle it all (in-detail - I already know the BIOS does it's thing first, then the OS and all that stuff... but that's a very generalized and basic understanding, not in-depth like I'd like), start talking about assembly and binary and binary trees and so on... figure I should probably find a university course for that though rather than asking on some forum though.

Currently I'm a geek that can fix 99% of issues, I know Windows like the back of my hand, but it's that last 1% that's advanced and requires knowledge I lack, and to know how to mess with those you have to know the deepest, lowest-level fundamental basics. That's where I teeter off right now.

That's why I was asking anyway, figured I could learn something here about how Windows does things - how exes are launched is kinda one of those fundamental things, and I'm surprised a simple registry change broke it, which tells me it must have some sort of dependency on some other process and I just broke it's bond to that. And figured maybe with that knowledge maybe I could come up with a solution. But I guess I may just go ahead and redo it now.