Even with 4GB of RAM it was slow. I didn't really watch movies or anything with it because it would sometimes lag out on 1080p content even with a dedicated GPU. It worked fine as a file server though until I started taking it to LANs. People hitting it constantly on DC++ lagged it out bad so it got replaced eventually. The Pentium D was just a very terrible processor. You also have to take into consideration that the machine I was using used non-ECC DDR2 and the speeds were 800MHz. So I had a lot more memory bandwidth in that machine as well.
I would look to Ebay for your DDR2 needs.
Kingston 2GB 2x1GB KTM2865 G PC2 3200 DDR2 400 ECC 2GB Memory Kit 2pcs | eBay
Wow.. it's such a good deal on Ebay. Thanks for the link. So the memory in your link is 100% compatible with my server right?