Don't even know what the problem

I believe i download something into my computer and everything became mess up.

I have NIS 2009 but it seemed did not working properly. It can only do the full scan until couple thousands files and it just finished.

I have download malwarebytes, superantipyware and avg antivirus to find out what is the problem.

at the first i scan the malwarebytes, it found some trojan horse file and i deleted it.

after I scaned my computer with superantispyware and it did not found anything. 

at last i scanned my computer with avg antivirus and it found a worm in my computer, but after i restart my PC, and scanned it with every software, all the software said my computer is clean.

But i still can not open some program and i can not do anything with my NIS 2009

I can not liveupdate, and i would like to re-install it but i could not unistalled the NIS 2009.

Btw I used windows XP and i use the original theme, but after my computer start for a while suddenly the theme changed into classic.

What did i do so that all the software did not work?

and i have scan in save mode too.