alright, I bought my computer in AUG 2002, it is a pentium 4 and it came with 512 RDRAM. I recently had a harddrive failure and I wanted to upgrade to a SATA harddrive so I purchased a new motherboard... motherboard gets here but the RAM slots don't match my RDRAM. My question is this: is my processor compatible with ddr ram or what else can I do? I've been without a computer for 3 months and now that I've dropped 200 dollars on parts I'm starting to freak out

As long as you processor is supported by the motherboard BIOS you will not have a problem. That 512mb of RDRAM will bring $100 to $150 on eBay. 1gb of DDR2 RAM goes for $75+-.