To make sure that the problem really come from the power supply and not from the power button of the pc case, We could use a power supply tester to verify that all the good voltage are present and that the power supply can take the load
Otherwise is you can't change your power supply yourself and do not wants to buy these video then you will have to bring it in a computer shop to have it repair.
If you just install a new software or driver, then go to Star - settings - Control Panel - Add or Remove programs and uninstall it from the list.
Once done try to Reboot in normal mode to see if the errors (Bsod) is gone.
3 = If you still get Bsod then you can boot whit a windows xp boot disk, and chose new install and when ask press F8 to accept License and then choose R to repair the install Windows. Very important to choose repair otherwise it will install a new copy of Windows and you gonna loose everything on you computer.Note: You will need you key number (License COA)in the process, so make sure you have it.