Windows 7 - Windows 7 says Operating System Not Found-- Help!

Alright, so this problem is a little complicated.

My computer fell a couple days ago, and I had to get a new hard drive. Unfortunately, my mother let my uncle who is NOT a professional install a "new" hard drive, which was actually his old one and came with Linux and not Windows.
It worked fine but I wanted Windows, so he did something and installed Windows 7 from a flash drive. And it was great.
Until this afternoon, when I accidentally changed the BIOS order and now I'm getting an "operating system not found" message... Is there something wrong with the hard drive (again, it isn't new) or did I just completely mess something up?

Hello lesharo, welcome to Seven Forums!



Have you tried setting the "BIOS order" back to what it was before you changed it?

Yes, I've changed it back to how it was but nothing changes, the screen still goes to OS not found.

Have your uncle check that the HDD connectors haven't come loose.

Okay I'll try that.
If it turns out that the connectors aren't the problem, should I just get a new hard drive?

Does the HD show up in the BIOS?

Boot the Windows 7 installer, select Repair on second screen, see if it finds an installation to repair and accept Repair. If it doesn't start up, boot back in to click through to Recovery Tools list to run Startup Repair up to 3 separate times with reboots: Startup Repair - Run 3 Separate Times

If this fails, try marking the Windows 7 partition active first before running Repairs: Partition - Mark as Active

It's possible if you didn't wipe the HD before Windows 7 install that GRUB code from the Linux install has corrupted Windows 7. Formatting erases nothing which is why it's always best before isntall to wipe the HD with zeroes to overwrite infected, bad or corrupt code: SSD / HDD : Optimize for Windows Reinstallation

By now you'll know if your HD is functional. You can test it using maker's diag/repair CD scan to be sure: Hard Drive Diagnostics Tools and Utilities (Storage) - TACKtech Corp. followed by Disk Check run from the installer Repair console Command Line.

If you wipe to clean reinstall here are some tips to get a perfect install if you want one: re-install windows 7