Hoo boy! Have you got problems!

What you have is 256 megs of memory overfilled with about 651.7 megs of
software. No wonder your windows are closing themselves.

Get a fresh copy of Hijackthis from here: http://www.merijn.org/files/hijackthis.zip

Run it and push "Do a system scan and save a log file" then post it here.
I'll pick a bunch of things for you to put a check mark on.