Well I am just going to go ahead and bet that your system is a 32 bit. If it was 64 bit, then it would say that when you bought the computer. 64 bit is a very new technology, and unless your processor is 64, then I would run 32.
If it is 3.1 GHz, I highly doubt it is 64 anyways.
I need to know more about what kind of processor you have. If it is just a Pentium 4 or something, then you have a 32 bit.
you can PM me with any other questions.
if you have a P4, you have a 32 bit processor. unless CLEARLY stated. very few P4s are 64 bit. and it would only be 64 if it was close to brand new.