I think he means P3 motherboard as in Pentium 3, not the model of PC.
Need to check the exact motherboard model you have, but P3 systems will run XP. Upgrade RAM to at least 512mb before you install it though.
3 gig drive will barely meet minimum specs for XP, and won't leave you much room for any programs.
With the money you will spend making that old PC usable you can find a used computer 20 times faster for about the same amount. A later generation P4 3 gig with DDR400 ram or even DDR2 RAM should be about $80-$100.