In the scene where you choose to go to map select, vehicle select, 
start race etc... type ENABLE(quickly) to be given access to all tracks 
and vehicles. You can now use all of the other cheats in the game... 
A sound should be heard for confirmation. First of all, when the race 
starts use F4 to cycle through the modes until CHEAT MODE appears. 
Then all the following cheats will become availiable:

F5 -Total repair (free).
F6 -Toggle Invulnerability on/off.
F7 -Adds 30 seconds to the timer.
F8 -Freeze/Unfreeze timer
F10 -Increment lap counter
F11 -Earn 5000 credits instantly
F12 -Switch between each opponents camera and your own. External view only.

SHIFT-F6 -Show opponents on map.
SHIFT-F7 -Adds 300 seconds to timer.
SHIFT-F8 -Toggle shadow between none/your car only/all cars.
SHIFT-F10 -Increment checkpoint counter
SHIFT-F11 -Lose 5000 credits instantly

CTRL-F8 -Toggle shadow between solid(faster)/translucent.
CTRL-KEYPAD 1 -Toggle fly mode - Use normal movement keys. Keypad 5 
places you on the ground(still flying). Keypad 9 and 6 changes the cars pitch.

Power-ups(still in cheat mode)

0 -Bonus
1 -Mega bonus
2 -Pedestrians glued to ground.
3 -Giant pedestrians.
4 -Explosive pedestrians.
5 -Hot rod.
6 -Turbo pedestrians.
7 -Invulnerability.
8 -Free repairs.
9 -Instant repairs.

SHIFT-0 -Timer frozen.
SHIFT-1 -Underwater ability.
SHIFT-2 -Time bonus.
SHIFT-3 -Oh dear, body work trashed
SHIFT-4 -Blow yourself up
SHIFT-5 -Frozen opponents
SHIFT-6 -Frozen cops
SHIFT-7 -Turbo opponents
SHIFT-8 -Turbo cops
SHIFT-9 -Gravity has gone strange???

ALT-0 -Pinball mode
ALT-1 -Wall climber
ALT-2 -Bouncey-Bouncey
ALT-3 -Oh dear, jelly suspension!
ALT-4 -Pedestrians shown on map.
ALT-5 -Pedestrian extro-bastard ray.
ALT-6 -Greased tyres
ALT-7 -Acme damage magnifier

SHIFT-ALT-2 -Instant handbrake
SHIFT-ALT-4 -Turbo!
SHIFT-ALT-5 -Mega-Turbo!!
SHIFT-ALT-6 -Blind pedestrians (to be used in conjunction with horn for a laugh)
SHIFT-ALT-7 -Pedestrian respawn
SHIFT-ALT-8 -5 free recovery vouchers.
SHIFT-ALT-9 -Solid granite car!

CTRL-0 -Rock springs!
CTRL-1 -Drugs!
CTRL-2 -Grip-o-matic tyres
CTRL-3 -Pedestrian Harvest