my pc was always crashing and i bought bitdefender total security 2009 and every time i connected do the internet it cought “something”, making the machine desperately slow and even crash sometimes. so i formatted the pc, installed windows again hoping that if i installed bitdefender before connecting to the internet it’d be ok, only i forgot that i had to download at least sp2 (for win xp) and windows installer, and the pc stayed just the same (or even worse). So in the microsoft forum i was told to format my pc, how to download all that i needed to upgrade offline and install comodo (he forgot that bitdefender also has firewall). and so i did. and comodo found a backdoor in /system32/lsass.exe but it couldn’t repair or delete it. it said it would be deleted on reboot but it’s still there. bitdefender found another backdoor and several trojans and ersed them, but it didn’t find lsass.exe!
and i still have the same problem…
i really don’t know what to do, i’ve spent €85 in a protection software and it didn’t solve my problem… 
is it the software? because when i was formatting the pc i had the internet cable on and only realized it about half way of the process… maybe that’s just it?
can you help, me?
thank you for your time, and excuse the bad english, please 