Computer getting stuck at Welcome Screen

Hey,

I own a Siemens Fujitsu laptop. I've been using it for almost a year, and suddenly now, it gets stuck on starting up. The welcome page, and the desktop come fine. ONE click, and everything gets stuck. The only way to shut down is to hold down the button.

I restarted in the Safe mode, which was working fine too . But later when I turned my laptop on, and selected the "Safe Mode" option, it went to the normal mode, and got stuck there.

But today, the safe mode came alright. Now I'm scared of turning my laptop off.
Should I reinstall Vista? How do I do that? Someone told me I couldn't do it without downloading drivers off the net, if so, what drivers should I download?

Would really appreciate any sort of help, thank you :)
I use Vista, Service Pack1