How do I fix Windows 7 OS

Please note that if a HDD is not recognized at the BIOS level then any tests, disk checks, or recovery tools will not find the disk either.
I suppose you are hoping that once this Hard Drive gets connected to another computer it will show life, but until we know that piece of the puzzle all of this other stuff is moot.

Don't get me wrong - it's all good information, just not all that helpful to the OP in the stage of testing she is in right now.

TVeblen said:

Sounds like a plan!

Keep in mind though, that any decent shop will test the drive for little or no charge. It is a 15 minute test - while you wait. They will be hoping to sell a new hard drive, should yours turn out bad.
Now recovering data, that is another story.

BTW- if you do need to replace the drive, see if you can go for an SSD. You will not believe the difference that will make.

I think I may just take it into a shop and get it tested, if they're willing to do it for minimal charge, or free. Given that I have one near by.. I'll have to check that out.

I think if I was more knowledgable of what I was doing it may be different but in all honesty, if you weren't explaining things so well I probably wouldn't have any idea what you were talking about. Haha. :)