I should start off by saying I'm pretty new to this tech sort of thing so bear with me.
I decided that I wanted to add more memory to my computer. It's a Dell Dimension E520 (DM061) and it came with 512MB of RAM. I bought 2 Crucial 1GB 240 PIN 128Mx64 DDR2 PC2-6400 modules. I removed the 512MB and installed the new modules in sockets 1 and 2. Now, when I check the system properties it shows I only have 1 GB of RAM and when I check the BIOS it shows socket 2 as empty. Is it a PCS-5300 vs. PCS-6400 issue? The salesperson told me my computer should be able to handle the 6400. Anyway, any ideas as to why I'm not getting the full 2G and why socket 2 is showing up as empty?
The E520's support up to 4GB Dual-Channel DDR2 SDRAM (533MHz); however, if you're using a 32-bit OS you'll be able to use up to ~3.5 GB. Regardless of the frequency you bot, you can install it in your mobo. Your RAM will only be able to operate at the limitations of the mobo. I am not very familiar with your model, but if there are four DIMM slots, then move one of your RAM modules to a different DIMM slot.