Sounds more like it is 5+ years old than "a few years old".
Anyway, that doesn't make sense since that model is an Asus pentium 4 motherboard. More information would be good:If you did not build it yourself, link us to the computer on the manufacturer's site. If you did or if it is a custom non-OEM build, continue below:
to attempt to identify the motherboard. (mainboard).
Depending on the motherboard, you may have a few options including the possibility of some of the lower powered Athlon 64x2 processors.
Why do you want a CPU upgrade?