Windows XP: PLEASE HELP!

PLEASE HELP!

Im going to try to explain this the best I can.
When Im running firefox, and I attempt to open a file to upload, (like clicking the browse button, to open the files)
firefox crashes, then restarts. this happens everytime, with internet explorer too.

now I thought I fixed the problem because I noticed my "Windows Search" on the Start Menu - All Programs. I noticed it when I clicked on it, it was missing.
So I googled it, and installed a new one (supposedly).
But that didnt change anything... I am still having this problem.
Its been happening for a few days now....I updated firefox, did all the updates for windows, and microsoft...and nothing has fixed this!

please help!
im running

Microsoft Windows XP
Home Edition
Version 2002
Service Pack 3

Compaq

**Ive also ran a computer scan with superantispyware, and it removed 9 threats or whatever. nothing changed still.

okay and its NOT only firefox, its my computer as well.
Whenever I try to open a folder or anything it closes and says windows explorer has encountered a problem and needs to close.

somebodyyyyyy please help me