Windows 10 OS disappeared from hard drive. is there a way to restore?

Hi, you can clean install Win 10 onto the 1Tb drive... but check the drive first. If the drive is failing, there's no point in using it.

E.g. Hard Disk Sentinel (trial) - great clear initial text report
HD Tune (free) - Health and Error scan.

And if you don't have full backups, you may want to try to recover data from it before clean installing. (Clean installing means you delete all partitions created when Windows was installed and install to unallocated space).

Activation of Windows should be automatic after you clean install. No key needed.

An outside possibility is you've lost the record of the partitions on the disk. There are tools you can use to check for that- once you know your 1Tb drive is sound.

Ok, if your C: partition was intact that could have been saved.

A great way to protect your PC, your data, and possibly your sanity is to routinely use disk imaging (e.g. Macrium Reflect - free + external storage for sets of image files). You can then restore a recent image of Windows or any partition or disk you've imaged when something goes wrong - even if you need a new disk. Recommend you start doing that when you're back up and running.

Another good idea is to keep as much personal data off C: as possible.

Another good idea is to keep as much personal data off C: as possible.

Hi, you have a desktop, so you could create a further partition on your system disk.
And you can install a further drive if you wish.

Now, that means you use files and folders on - lets call them D:, E: respectively.

You then have at least these options.
a. Create new libraries on D: E: and use those.
b. Create folders on D:, E: and add them to Windows' default libraries
c. Relocate existing libraries to D: or E: (Properties, Location tab).
d. Simply create folders on D:, E: - and do nothing further about libraries

Of these I'd personally never use (c) as people sometimes make bad mistakes doing that. Others are happy with that.

What's different about option d? If you have several users or logins for the same PC, you would probably want to keep their data separate- and libraries can help in doing that. Option d: would most likely mean- unless you manually set permissions- anyone logging in has access to that data.

Clearly keeping personal data off C: means maintenance of the OS has the least potential impact on your data. In particular, if you restore a disk image of C:, that means any data on C: is now that which existed when the image was created (= older or the same).