Press "start" (bottom left hand corner) and then "run".
In the box, type in "msconfig".
Along the top there are several tabs - the 2nd from the right should be "start up" - click on this.
This shows you what programs run whilst your PC is starting up.
I can't really help much more soz - you need to work out which one it is and de-select it from the list so it doesn't start up when your PC is booted up.
Hope this helps.