Boot loop (I think)

My Friend was having trouble with his Computer so I offered to fix it. I thought I could handle it but I am stumped...

Well, I JUST installed a fresh version of win Xp on it, and now it will say that the system was not shut down correct ect. When I click run windows normally it just reboots.

I tried the HDD on my computer and it works fine.

I think it is a 2003 or a 2001
HDD- Seagate Barracuda 40gig
I dont know much else about it but im sure I can find out if you need it.

If someone knows what the problem is and could tell me that would be great!
If you don't and you could make a suggestion that might help that would be awesome also.

Thanks in advance

-Luke