Dell Dimension Model 4600; Intel Pentium IV; 2.8GHz CPU; 256MB RAM; 80GB 7200RPM disk drive; CD-R/W drive; Windows XP Pro; 15-inch NEC Multisync 1525M LCD Monitor; and Logitech wireless keyboard and mouse.Well, you didn't mention what the graphics card is, so I'm guessing it's an Intel Integrated, using shared memory. Bad news if you want to play Halflife in its full glory. A memory and GFX card upgrade would be a perquisite, though if it's working fine now, maybe just a memory upgrade would do.
Not too bad though, new computers are always nice.