Computer very buggy - not malware

hey. I tried posting on maleware removal forum twice after doing the procedure, but got reffered here, saying my problem is software related.

Every time i open the computer i get a "windows explorer has encoutered a problem..." error. I cant open any explorer feature, as in internet (using firefox works), my computer, Outlook express, or any folder from the desktop. sometimes drwatson debugger appears with an error.
Once in a while, the Windows Explorer error would still be around (since every time i press "close" desktop reappears with the same message), but i'll be able to use most features normally. Rarely i open the computer and not get a message.

What is this bug that has moods, mostly appears blocking any work on the pc, or appears and doesn't interfere, or does not appear at all?

I use windows xp sp 2 with automatic update enabled. I also keep it clean with ccleaner and defrag with IObit.

Will appreciate any bit of help or information. Thanks!

 

Does it happen in Safe Mode?

 

i've tried safe mode once and it seems to work fine, glitch free.

 

Test it under these conditions.

http://support.microsoft.com/kb/310353