Hello Uriah,
this is quite old technology for a PC, and the Celeron proc. is one of the weakest in performance. I had OFF Phase 2 running on an AMD 3000+ with two Gb of Ram on an Asrock mainboard, and with an ATI 9600 Graphics card, and it worked - but there was stuttering above airfields, not a slide show but close. Any slower single proc. will probably not make you happy.
Cou can get much better PCs here in Germany for say 300 Euro (don't know exactly what this is in $$ ?), with a 2x2300 Intel dual core minimum and all you would like, so...
The most important thing apart from proc. speed is the internal clock Ram speed, and of course the graphic card. I take it in the PC you described this is even an onboard graphic chip stealing its Ram from the system memory.
Greetings,
Catfish