OK if you are getting one beep it is probably the video card. One beep means that everything soldered to the motherboard is OK (including the RAM and Processor - which aren't soldered to the motherboard).
If you do not have graphics then maybe you just installed a new video card? Is video coming from it now? Do you have a seperate video card or is it "onboard" (does your monitor plugin by the mouse and keyboard?)
You are probably not getting any beeps when you move the RAM because some mother boards require that RAM be installed starting with the first slot (this slot is usually closest to the processor (which you can recognize by the big fan on top of it)). If the RAM is not in the first slot than your machine will not POST (Power On Self Test), and will not beep.
You can always go down to your local Computer store buy a cheap video card that works with your computer. Plug it in. Plug the monitor into the new video card. If you now have video, it's the video card. If you don't still don't get video return the card, and just tell them it didn't work (don't tell them you were using it to test your computer!
If it works and you don't like the video card you just bought, take it back and exchange it for a better one. The store should have no problems with that.