XP user accounts

Hey guys, (on behalf of a friend) a new problem for you to puzzle:

I installed halo pc no problems (pc meets all requirements of game) but when i try to play it it says that i need admin privilages, which i have got!
I am the only user on this pc and am ADMIN.
I get the same problem with windows update, safe mode does nothing to help either, windows update always displays this (screen taken in safe mode with networking enabled)
Any idea's on a fix (i *really* dont want to re-install) ?

Thanks in advance,
TRP

 

*bump*

 

What does XP say under 'user accounts' in the control panel?

Might have something to do with being on a network. Network policy settings? Don't know. I'm not on a network.

 

'Morning all! I'm the friend that TRP talked about, thought I might need to sign up to check replies 'cos he's gone of to Cyprus for a week!

There is only one account on the machine, and that is admin. All the other machines on the network have no problems with updating or games.