Hi Bob,
I have emailed you, it normally happens if you have a pagefile error.
So the quickest/easiest way to solve it would be to use LAST KNOWN GOOD CONFIGURATION, but this doesnt always work.
You have to check that you have enough HDD space when you do get it to boot though as this can be a contributing factor.
Re the GPU drivers.
You uninstall the old display driver from add/remove programs in control panel and download the latest one from ATI Graphics Drivers & Software
and then restart, when the PC boots run the exe from wherever you have saved it to and when its all installed, restart again - done :)