hi ,does the computer bootup at all ! if it does what happens ,and how do you know it the video that is causing the problem, if it boots up but has bad graphics ,maybe you just need to install video drivers .
as for getting new GMA 900 graphics processor that would involve changing the motherboard,or PCI conventional video card

video drivers here if needed .
http://support.gateway.com/support/d...&param=1008602

The computer comes on but you can't see anything on the monitor, I have tried to use a different monitor to no avail. It's like the monitor isin't hooked up, but it is. I have no clue what to do, any advice would be great.

hard to help with that ,because it could be anything ,actuall it could be a bad power supply , or ram even ,do the cdroms open ,can you hear the windows sounds if enabled ,do you hear the harddrive running .

The disk tray opens and I can hear the hard drive spinning. Wouldn't the BIOS still come up if it were anything else? Is there a process of elimination I can use to narrow it down?

you could open the tower and unplug cd drives ,remove any pci addin cards if any, remove ram ,and then try and boot.if it make beeps because of missing ram reinstall it ,if you have more than one stick of ram just put one back in and try again .
a power supply going bad can cause it to only half boot up!

would anything show up on the screen if it were the power supply going out?

NO! ,thats what im trying to tell you .it could be a lot of things besides the video , I have replaced dozens of power supply that will power on but not boot windows fully and show anything on the screen ,I use a power supply tested to check the psu, before i change it !

Ok I will do as you suggested and unhook the cd-rom, and take out both sticks of RAM and reboot it, then if it beeps I will put only one stick back in and try again. Then I guess I'll get back on here. Thanks for the advice.

I agree with the others that there are things to look for before suspecting the internal graphics.

If it isn't anything else based on the foregoing advice, then I suspect that you can add a cheap PCI graphics card after finding the motherboard bridge that must be pulled to disable the internal graphics. I can't guarateee that this particular motherboard has this facility, but it should.

Finally, just a sanity check - you obviously think it's booting up OK with no display. If that was the case, you'd see the keyboard lights flash early during booting and you'd hear the whirrs and clicks and see the disk led going for the usual amount of boot time. Presumably also you can enter your windows password at the right time and see more disk activity. Yes?