Non-great PC mind seeks help on ATI 4800 series

Hello and thank you,

Just to reiterate, I am not very knowledgable when it comes to PC's so you may need to explain things a little to me.

After finally getting my 3 year old down for a nap I permitted the other child to have some Wii time and looked forward to having some computer game time myself. Magically (at least to me) however it seems that I am unable to play any game that does not operate on the desktop. What happens is that the screen goes black and stays black. The fans and such of the computer continue to operate as though the OS is still functioning. I do not hear sound from my speakers.

I have not installed any new hardware. I have recently installed a new game off steam. I have recently uninstalled and reisntalled steam. I have uninstalled, swept (via guru3d's program), and updated graphics drivers.

My best guess (again) is that the failure is occuring either during 'real' GPU operation or when the resolution is being tweaked.

My faults at this time seem to be either Gfx card, PSU, or monitor. I do not know how to trouble-shoot it down to one of those items.

All thoughts are appreciated and thank you in advance,

Eric