I have read the stickied post at the top of the page and have done some research of my own, but I'm still not 100% sure of some things. No better way then to ask!
CPU-Z and Crucial both say i have DDR PC-3200 Memory. Belarc, which is a little cryptic to the unknowing has this information.
1016 Megabytes Installed Memory
Slot 'DIMM0' has 512 MB
Slot 'DIMM1' is Empty
Slot 'DIMM2' has 512 MB
Slot 'DIMM3' is Empty
I currently have 2x 512mb memory sticks installed as you can see and am looking to upgrade. My main question is, can I install 2x 1gb sticks to have a total of ~3 gigs of ram or will that be incompatible?
Yes you can fill the empty slots with memory up to what your motherboard supports. Check the manual to see what sticks are supported.
Check for the maximum memory supported by your motherboard.
I think you are fine with extra 2x1GB sticks.
Buy DDR-400 or also called PC-3200.
Yes it should work, only computer of venerable age didn't support asymetric RAM (DIMMs of different sizes). As evongugg said, make sure your MB supports 1GB modules (if maximum RAM for the MB is 4GB, it does; 2GB, it might not). When you install the RAM, check the MB's manual to know what DIMM to put where to make sure it still runs in dual-channel mode (could be 512 - 1024 - 512 - 1024 or 1024-1024-512-512 or ...).
However I'm unsure what the computer jargon means.
From the above link.
Rules to Enable Dual Channel Mode
To achieve Dual Channel mode, the following conditions must be met:
* Matched DIMM configuration in each channel
* Same Density (128MB, 256MB, 512MB, etc.)
* Same DRAM technology (128Mb, 256Mb, or 512Mb)
* Same DRAM bus width (x8 or x16)
* All either single-sided or dual-sided
* Matched in both Channel A and Channel B memory channels
* Populate symmetrical memory slots (Slot 0 or Slot 1)