Help! Virus Don Catch Me O!

A COUPLE OF WEEKS BACK, I OPENED A FLASH (THAT PROVED TO BE INFECTED WITH A VIRUS WITH A CRAZY NAME I CAN`T READILY RECALL, BUT IT HAS A .AVI ENDING) ON MY SYSTEM.
SINCE THEN I`VE BEEN SEEING A LOT OF STRANGE MANIFESTATIONS, VIZ:

1. THE SYSTEM HAS SLOWED DOWN CONSIDERABLY.

2. IT IS FAST BECOMING INCAPABLE OF RUNNING MANY APPLICATIONS CONCURRENTLY (I AM A GRAPHIC DESIGNER/WEB DEVELOPER + GAMING MAJOR).

3. TASK MANAGER DOES NOT SHOW UP ANY MORE (EVEN IF I PRESS ALT+CTRL+DEL 1 MILLION TIMES)

4. REGISTRY CLEANER IN TUNE UP UTILITIES IS NO LONGER WORKING (I`VE HAD TO UNINSTALL IT).

5. WINXP MANAGER IS NO LONGER WORKING

6. TO CAP IT ALL, MY ANTIVIRUS (AVAST PROFESSIONAL 4.7.1029) IS NOT SEEING ANYTHING NOT TO TALK OF CLEANING IT UP.

DOES ANYONE KNOW OF ANY ANTIVIRUS I CAN USE WITH GUARANTEED POSITIVE RESULTS OR ANY OTHER TRICKS I CAN TRY (I`VE TRIED RUNNING SYSTEM RESTORE BUT THE SITUATION IS STILL THE SAME.)

P.S. I CAN`T EVEN THINK OF FORMATING THIS SYSTEM BECAUSE A SIGNIFICANT PART OF MY LIFE IS ON IT AND IT HAS SOME PROGRAMS THAT ARE DIFFICULT TO COME BY.

kaspersky or nod 32.because an antivirus is free does not guarantee its efficiency thats why avast is crap!

Simply copy all your files(into your flash disk or whateva) first of all, and FORMAT THAT SYSTEM, that's all i can tell you.Get Panda Anti Virus or a licensed McAfee, i get the licensed one if u need it contact me
Adios'

The best option is to get Bullguard antivirus ,  You can download the free trial if u need the full version let me know ok.Its your only solution my dear brother trust me I have been there before in your situation. try it and let me know.