Blah when you turn on the computer what does the monitor actually say? Is it just black or can you see the PC Post but when you get into Windows its blank.
If the monitor is blank from the time you turn on the computer pull out the VGA cable. If the monitor displays text your videocard in the PC is pooched. If there is still no display try a different monitor.
If its just once you load windows. Shutdown the PC and reboot while tapping F8. Log in and goto the Control Panel and to Display Settings and just click the Apply button and then reboot it yet again
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