well what does it do. if u can still use ur PC fully then its not windows its self, its probably a program that starts with windows.
Try going into start and run, then type MSCONFIG.
Now go to services tab and tick "Hide all Microsoft services" and untick a few of the services and start up items (in the start up tab) click OK then reboot see if it comes back then if still then re-enable them a try another lot until u can narrow down to which one it may be.
Then seek help to fix the start up item.