Installing powercolor 9550 on pcchips 810...

I have installed a 128mb ati radeon card on my pcchips 810lmr board which has an 1800 athlon and 512 ram on it. The ATI drivers won't install and they display an error message which tells me an administrator must install the drivers even though I am in as an administrator. The windows XP vga drivers won't install either as the error message I get says that the parameters are not correct. I have tried disabling the onboard graphics and have tried as many different drivers as I can find but none will install, when I first installed the card it would not work until I plugged a power supply into it direct.
Any ideas