Windows Vista Business Edition WON'T ACTIVATE Help please

Hi

From my college I got the Windows Vista Business edition with a legal serial
number. So, I formatted harddisk,and did a clean install on my pc.

Everything seemd to be okay but when I try to activate I get all different
kind of error messages. Like "The RPC server is unavailable" and "The service
is not started".

When I try to start the service called "Software Licensing Service" and when
I try to activate it crashes, a pop-up comes up and says the software
licensing service stopped working (then you get a message like 'Ask microsoft
online help' and that kind of things. But nothing seems to work.. I can't
understand
Now every time "Software Licensing Service" crashes.

However my serial number is a legal one, so thats not the problem.

Hope for an answer, thanks.