Computer Turns on - No Response on the Monitor with two different video cards, is it the motherboard?

Gateway Computer - a friend of mine asked me to take a look at his Gateway tower. He said he went to use it this morning and the monitor wouldn't turn on. I tested it on my monitor and had the same thing. I changed the video card with mine still nothing. The computer turns on but does not beep or anything and does some "thinking" then stops. The numlock on the keyboard will not toggle off from the on position. I've tried running without the hardrive. Removing cmos battery and discharging the power is the step I'm at now waiting to see if that will have an effect. I'm figuring the motherboard is bad. Is there a good test to see if thats the case? I think I'm going to have him bring it to best buy and having their guys look at it. Any suggestions would be greatly appreciated.
fisher123Asked:
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michkoCommented:
Extremely difficult to troubleshoot without any video output.  I'm attaching a link on troubleshooting a blank monitor, but appears you're already done most if not all the steps.  And yes, they end up with if still blank after replacing with a (known) working video card to take it to a shop.
http://www.smartcomputing.com/editorial/article.asp?article=articles/2007/s1801/25s01/25s01.asp&guid=
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michkoCommented:
And yes, sounds like a mb.
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A1opusCommented:
Is there any beeps? If NO then put off the CPU and clean it and then reinstall. Otherwise, its a MB problem.
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