with that setup you should be able to run all games @ 1600x1200 no problems. Make sure you went to add/remove programs and uninstalled the radeon drivers. Boot into safe mode, see if all instances of the radeon are gone in device manager under display adapters. Reboot.
Right click on desktop, settings, advanced, geforce 3, here it will show you all the drivers being used. Make sure it says 21.83. Also go in d3d settings and open gl and make sure vsinc is off. It sounds to me like the driver is not installed right or there are some Radeon ghosts in there. Let us know if this helps.
Celeron 633 @ 1064 , Windows XP server,
Pentium 3 1000 @ 1100,Abit bx-133, 256 Mb Mushkin Rev.3 cas 2-2-2, ATI Radeon
AMD Thunderbird 1.4 @ 1.63 (24/7) IWILL KK266R , Corsairs pc 150 cl2, Leadtek GeForce 3