Windows Protection Error

I have just installed a USB PCI expansion card to my PC. I restarted my PC and it detected the new hardware and prompted me to install the drivers for the card. I did this and it said that there is a newer version of the file/s on the computer and it recommended that i keep the existing files. I did so, however when i now attempt to start the PC i receive the error message “Windows Protection Error – You must restart the computer”. I do this and it prompts me to go into safe mode…blah, blah, blah…
I have tried a step by step startup and bypassed the autoexec.bat file as it says to in the “Windows Help – startup troubleshooter”, still no luck.
What steps do i need to go through (please no URLS) to find my problem and fix it!

Cheers!