Probably that shoddy Athlon workmanship again.
Man that speaks from arse
I've got a Athlon 1700, 256Mb RAM and GeForce 4 MX 420
That should be well up to spec for this title. You say Athlon 1700 so I presume an AthlonXP but you dont say the ram type so I'll assume PC2100. The G4MX aint going to help with that Doom3 alpha but is more then enough for a game of UT2003.
Check the aperture size of the AGP bus (set it as high as stable, probably 128MB with 256mb ram),
Permanant swap file (virtual memory) of 768mb,
latest drivers (
www.nvidia.com) this is the detonator 40's, and for gods sake, turn OFF anti-alaising.
also turn off any other resident services like firewalls, virus checkers blah blah blah.
Use msconfig (from Run in the start menu) to kill off unnessecery programs / services at startup.
Via or SIS chipset? Update mobo drivers, especially for a via board, this gets a lot of extra power from no where.
If all else fails:
www.overclockers.co.uk
Their prices are only just off trade (about 5% profit margin after VAT) and throw more RAM at your system.
Oh, and stop running it at 1600x1200 32 bit. I have a 2ghz P4 with 1 Gb ddr pc2100, cas2, Gforce2 64mb ddr(the weak point), winxp and 7200rpm IGM 120GXP drives. 1024x768 gets me 120 FPS at 32bit which is more important then funky hi-reso mode.
Take two pills and if you get any problems, call me in the morning