I have set 3 different copies of this game up on 3 different systems:
My own:
Athlon 900mhz
384 ram
XP Pro
GF3 Ti200 (default clocking)
SB Live!
(XP D8 patch)
On this config, at 1024x768 32bit colour (max detail) and Quincux antialiasing the game is extremely playable (and smooth). Turn off Quincux, and the game gets even smoother.
The only things I have tweaked is the OS (turned off all un-needed services), and I have copied all the Audio files to my HD and installed the NO CD Crack. This stops the game jerking momentarily when changing radio stations.
Friend 1s comp:
P3 500
GF2mx
Win98se
196ram
SB PCI 128
(no background tasks bar explorer)
I am not going to pretend this game is silky smooth running on the said configuration, but the average framerate of 20FPS (tested with fraps) is well playable.
Friend 2:
P3-850
GF2 GTS
Win98se
SB Live!
(no background tasks, bar Explorer)
All details on max at 800x600x32 and the game runs smoothly for most parts, jerking only a little when police chases get more involved.
The biggest tweak for performance in this game (mostly on my friends systems) was to enable Direct Sound Hardware Acceleration in the sound options, and copying the Audio files to the HD.