Hi Chris
Without knowing the problem, this sounds like some kind of spyware that is interfering with your registry.
Try using Spybot Search & Destroy from http://www.safer-networking.org. Download it install it, update it, immunise and run a scan. One of Spybot's tricks is to restart your computer (with your permission) and to then get in ahead of any spyware before it loads.
When it is done, you may need to reset your antivirus.
Also, take a look at startup monitor from www.mlin.net which will tell you if any software tries to change what happens when windows starts and can stop things changing without your permission.
Peter
October 2007