CPU constantly at 100%

Being as stubborn as I am for Windows 7, I waited until the last possible second to upgrade to Windows 10. Now that I've upgraded, my CPU is constantly at or near 100% mainly by two processes listed as System and System Interrupts, both running 20-30% each. I looked around and most people say these shouldn't be more than 5-10%.

Before you start suggesting the obvious like checking for updates, flashing BIOS, upgrading drivers, editing Registry, using Process Explorer, going into device manager, checking background apps, using the built in troubleshooters, formatting, erasing previous Win installations, etc. Let me just say, that I've tried all of those and none of them seemed to work. I can get the CPU down to about 50-60% but that still seems like quite a lot for a freshly booted up PC just sitting on standby.

At this point, I'm looking for any suggestions at all. My best guess is that maybe my laptops just too old? I've had it for close to 5-6 years or so and I never replaced any of the parts, so it may just be that it's just getting harder to run modern OS? I don't know. If there's any other options, I'd love to hear them before I start looking into replacements.

Welcome to TenForums. I looked up the specs for your computer and I see that it is a 4th gen core i3 CPU. While not a speed demon, I might note that I have an old laptop that has a much older CPU and it's not getting hammered the way yours is. Granted, I have twice the RAM yours does, but the point is that a lot of older system still run Windows 10 just fine.

It sounds like you have tried a lot of things so I'll try not to cover things you have already tried, but if I accidentally hit upon things already tried, my apologies.

Have you tried to boot into safe mode to see if the processor utilization is also unusually high? If not, it may indicate that something installed is at fault.

I would also suggest uninstalling / reinstalling any antivirus / malware scanning programs. For some reason, those seem to often be the source of problems after an upgrade.

Finally, if you make complete system image backups of your system, I would like to suggest simply trying a clean, fresh install on Windows 10. I know that this one takes some effort but it can reveal a lot. If a clean install runs well, then you know that you are dealing with something in the current install. On the other hand, if even a clean install does not run well, I would be less optimistic at that point. When done with that test you can always restore your full image backup.

I hope this at least gives you a few ideas.

Good luck!

Thank you for your help! I already tried booting into safe mode but that didn't seem to work, but I haven't tried reinstalling antivirus; I'll see if that doesn't help.

I'm typically really paranoid about blue screen crashes so I tend to keep all my important programs and files all on external drives anyways so it's not that big of a big deal if I can't seem to fix it. It's not going to ruin my experience to put up with slower performance until I can get a more permanent solution but thank you for your help. I really appreciate it.

I like TC's suggestion. It's a lot less drastic than my suggestion of uninstalling / reinstalling. Simply disabling it would be a much easier way to determine if it is involved.

I have a tendency to use the "big hammer" approach a little too often

There is nothing like a clean install.
As you have 4G of memory and internal graphics my suggestion is to install 32 bits version.

This page gives many suggestions about 100% disk usage: 100% Disk Usage in Windows 10 Fixed With 14 Tricks