you may want to try another antivirus program with higher detection rate, such as avira free edition, just to be absolutely sure, as it sounds like a virus
if there are no instances, its a corrupt system file
vista is notorious for that
the easiest thing to fix that would be run windows update, and update your computer
if you have already downloaded all updates and service packs available to date, try a clean reboot
hopefully its not a system file, and its a 3rd party application
to check this:
click start
type "msconfig" in the search bar
right click and click "run as administrator"
there you will see "startup selection"
click selective startup and uncheck "load startup items"
next, in the services tab, check "hide all microsoft services"
then click "disable all"
now click "ok" but before restarting click on START then type CMD and right click to run as administrator
open 2 of these windows
in the first cmd window, type "sfc/scannow"
in the next window type "chkdsk c: /f /r"
then type "Y"
this will check and repair errors found
see if you have the same symptoms, if not, check each service and startup program one by one to see what is causing the problems
if you are having symptoms, contact me at jake_jake36@yahoo.com and i will give you more instructions
im not a spammer, im just bored
haha