Well call this fate.This is what happened first my i cannot connect to my internet because of some 'line' problem then at that time my anti virus which is a trial version (Quick Heal) gets expired, i was reinstalling it every month since it had a one month validity but know i do not install it again thinking since i have no internet connectivity there is no threat of virus.But my friend brings a flash drive to do some work & with it probably some virus then the next day the destruction starts my PC takes a long time to boot then after that some programs are not working then i realize something is wrong & i try installing Quick heal it detects virus during pre install scan & requests a boot scan so i agree the PC reboots & boot scan takes place which destroys over 1500 .exe & other files including many of essential softwares like office 07 matlab_7,games etc some of the files are like setup.exe then finally after all this i reach the welcome screen then slowly one after other icons appear after that i try top install quick heal but it requests another boot scan so i reject this time then i reboot try to enter safe mode but the pc reboots when i select it, i try again with same results.All this while i still don't have internet connectivity so cannot get any help.The next day when i boot my PC after reaching the desktop i get the message 'Microsoft corp. closed this program for safety "eplorer.exe" 'i am left with the blank desktop no icons no taskbar .I am using multiple partitions so i format my windows partition then i install avast pro then i install some more programs like adobe reader & all drivers i am left with very few programs as quick heal deleted the rest.Now i do a full PC scan with avast it detects over 1,000 files but all in 'system volume' of different partitions & some in other folders i bring office 07 & other utilities from my friend & install them now the PC seems to work fine & a few days later my internet connection is working so i download some more programs such Firefox,vlc player etc. Now i want to know what had happened to my PC am i clean now? Quick heal detected 'win32.sality.V' during boot scan & avast pro detected 'trojan.slugin' sad part is half of my games are gone now because the .exe files have been deleted but some are working why is that ? Some softwares setups are working other are not why is that ? How to prevent such things in future.I also scanned with malwarebytes antimalware it detects nothing. specs: Intel core 2 Duo 2.8 Ghz 4 GB DDR2 RAM 512mb nvidia graphics card 250 GB hard disk - i have made 4 partitions Before: Win xp sp3 32bit Now: Win xp sp2 32bit Sorry for the real long post but wanted to tell you guyz what exactly happened. Thanks for any help.