Much like a porcessor, there are ways to over clock your ram. I dont know them personally, but i know it can be done. This porcess will more than over heat your normally equipped hardwear though so i wouldnt suggest it unless you feel like getting a liquid cooling system or a few pci/case fans to get the air moving and reducing the inturnal heat. If you dont feel free to just take a blow tourch to you motherboard and ram because itll have the same effect.
your best bet is to get faster ram or a new computer ( there is no was to change the pc speed of your ram unless your down grading pc2700 will run at pc2700 unles you pair it with a pc 2100…. Then it will run at pc2100 speed and more often than not, the ram you have is the top pc speed for your motherboard.) Options, get a new computer or just settle with what you have.