Computer turns on, monitor says "no signal"

Hello,
I have been using this computer for around 4 years now. I recently had problems of it randomly turning off at any time, I could be working on a document, or the computer can be just sitting there, and it would turn off randomly.

I fixed that problem by backing up all my files on an external hard drive and simply reformatting. I was using a Wireless B PCI adapter for internet before reformat. Because of the reformat, it got uninstalled. So I took it out and installed it on another computer (which is liek two years older) because the modem is right beside this computer so I decided to run ethernet.

On the older computer, after installing the PCI card, the computer would turn off and go to a blue screen saying there is a hardware issue and stuff. So I would boot to last known good configuration and the card wouldnt be installed, so obviously there is the problem.

I took the PCI card out of that one and put it into the 4 year old computer to see if I would have the same problem, I didnt. Everything worked fine. I switched locations of the computers so one can use ethernet and one can use the wireless. After switching locations, the 4 year old computer did not work. It would turn on, fans are spinning, no beeps or anything, but nothing would display on the screen. I tried sticking in the xp disc so I can boot from that. I tried removing the hard drive. Nothing helped. No BIOS, no video. Then I decided to take out the wireless B PCI card, then the computer booted!!!!

No files lost or anything. The reason I wanted to fix this computer so badly and not jsut get a new one is cuz I just bought a geforce 8600 so I can hook it up to my projector with good quality. After installing the graphics card, I have the same problem. The computer starts, the fans are spinning, everything, but the computer wont load. No BIOS or anything.

I took out the Graphics Card, hoping it would boot like last time, but it didnt work this time.

Yesterday, I took out the battery for 30 seconds hoping to reset the BIOS and I replaced the RAM. Now I turn it on and the screen goes crazy. Lines going everywhere and stuff!!!

Yes one more thing, with this computer, when I turn it on, the fan goes hyperspeed for 5 seconds then calms down, its always done it, for the last 4 years! Now when I turn it on, both fans work, and the one that goes hyperspeed keeps going at hyperspeed.

O and yes I have tried multiple monitors. The one I am using right now works, but when plugged in to the other computer, it does that crazy screen thing.

The 4 yr old computer has integrated graphics, this is why I want to install a graphics card.

I have a gateway 420GR.
K I don't think I am forgetting anything. Please HELP!!!