|Try reseating the RAM modules. Make sure they click into place and click into the brackets. Then, go to Start > Run > type: dxdiag to open the DirectX Diagnostic Tool and report how much Memory it has listed.|
P.S. It's unlikely you're using a 64-bit version of Windows XP. The 32-bit can only support about 3.2GB of RAM. Running Windows XP with only 2GB is very good.
Apologies if I don't respond to your reply immediately. I don't check this site daily.