Joerod,
Speaking as a server guy, your "free" server may end up costing you in the long run. It's a circa 2001 Dual-processor Pentium 3, with 133MHz (not GHz) RAM, Ultra SCSI 3 drives, 100M ethernet, and PCI/PCI-X slots all in a 7 RU chassis. No offense intended, but these days we call that a 13 year old space heater. The amount of compute capability vs the amount of power being used is quite disproportionate compared to even inexpensive modern hardware. To be perfectly honest, most modern smartphones have more horsepower...
I don't want to dissuade you from using it, but you may want to set your expectations appropriately... Also, keep in mind that if you start to use it for "production" purposes at home, you are running a higher level of risk. Your likelihood of getting spare parts is slim, and those disks are around 13 years old. In the enterprise space, 3-5 years is considered old for disks, and 5-7 is considered old for server hardware. New hardware uses less power and has on-average double the performance of two years previous.
Just wanted to set your expectations relative to your hardware's capabilities...
Hope that helps!
/Mike