Look for a model number on the front of the computer or on the side (not the WIndows number though).
Or, right-click on "My Computer", scroll down to Properties, and copy the information from there. The first screen should give info on the CPU, memory etc.
Pentium(R) D CPU 2.80 GHZ
2.79 GHZ 1.00 GB of RAM?
Is that helpful?