I don't use windows, but generally there are three categories of stuff on your computer
(1) the operating system
(2) the additional software
(3) your documents

The operating system is something that you can delete/upgrade/reinstall any time. May take work, but there's nothing irreplaceable about it to worry about losing

The additional software like MS Office you mentioned is similar. Since you bought it, you should be able to download it again and reinstall it.

The documents (including pictures/movies/music) you've stored on your computer are the most important thing you probably don't want to lose. I think on typical systems Win/Mac they are intermingled on the same disk space with the operating system. While changes to the operating system like upgrades shouldn't be touching the documents more drastic measures like reinstall may delete them irreversibly (depending on how it's done). On a typical unix type of system those documents would reside at least on a separate disk partition or even separate physical hard drive so whatever you do to the operating system and the software doesn't touch the documents.

I realize this doesn't help you with the problem you're facing, but hopefully gives you some idea of some things you should be careful about as you're trying to fix it.