Every time I log on I get multiple messages telling me certain programmes can't be opened. I open firefox and hundreds of windows open up all by themselves. When I close them the tabs in one window start opening up themselves. There is no load bar in the corner either. I don't know if its a virus or what, a norton security message comes up and says it can't be run to scan messenger or something. I don't know what's going on. Any help would be appreciated.

Sounds to me like a virus. Try running some free AV apps like AVG and Anti-Vir. After that try running Spybot and Ad-aware and see what that turns up.