It's possible that this is a left over registry key from a trojan that has been removed. Analysis using a HijackThis log would be best to sort this out.
We have a security specialist (Essexboy) who will help you on this, but you will need to download HijackThis and run it to produce a log. Then copy/paste the log into your next post.
You could also consider registering at Virus Vault for experts to deal with it.
http://www.virusvault.co.uk/fusionbb/fusionbb.php?(Wait for Essxeboy first though, he should be along later today.)