I haven´t got Rayman 2 myself, so I don´t know if this will work, but try:
1) Run the game as Admin (right mouse button > Run as Admin)
2) Install it on a path that is not C:\Program Files. If it was there, try another path
3) Disable any antivirus you have, even if it´s only a expired trial
4) Change the resolution AND restart the computer, try it multiple times as some people report it worked after a reboot and some errors afterwards
5) Put W98 or WXP compatibility (right mouse button > Properties > Compatibility)
6) Try to run the game with the exe and with the shortcut. It shouldn´t matter, but one of the times I run Rayman Forever by the exe my saved game wasn´t there. After starting by the shortcut, it was.

It *should* work with one of those things. Maybe it´s a mix of some of those.

What OS?

What error message(s)? (Try to start it in a terminal to get output messages).

Well nevermind but thanks anyway guys. I couldn't get it to work on my laptop(Alienware M11x R2 with Windows 7 Home Premium 64-Bit, for those that have it beware). It worked once but i couldn't get it to work at all really.

It is now running flawlessly on my custom desktop with Windows Vista Business 64-Bit, no tweaking needed at all well except for changing the resolution to make it look nicer)

My bet would be the video drivers on the Windows 7 machine. Some vendors (such as HP, Dell) customize the drivers for some of the hardware (such as ATI or NVidia cards, sound drivers, etc.). You could try and install the latest driver from the video card manufacturer, not the laptop manufacturer.