Right, I previously had this problem when installing the game (CE), as probably everyone does.
I then used the usual assortment of fixes to sort it all out. No problem.

However, I have recently installed some new drivers to counter an issue with a different game, and now my game is REALLY fast.
The game clock in the geoscape still ticks along nice and slow as usual, and the globe rotates just as nice and slow too, but everything else (menus, scrolling etc) is fast as hell.

In a way, it's kinda cool.
Explosions and smoke looks a bit better, I think. And autofire is about as rapid firing as it would be in real life (pew-pew-pew!). But the problems outweigh it. Firstly, if there is alien/reaction fire, it's impossible to tell what it was, where it was from, or even what got hit.
Secondly, scrolling around the map is a bitch.

I'll ask the obvious question first: Did you change the settings in the in-game options screen to slow things down? If you did that and everything is still fast, check out one of the many Slowdown Utilities. I have my doubts that these would work as they slow down the CPU and not the video card, but it can't hurt to try a few. You could fool around with some of your video card settings to scale things back. What I do to play the games is disable my video card completely via the control panel. That forces the game to run under the legacy drivers which shouldn't cause speed issues.

- Zombie

Hrmm, I don't suppose there's a way to disable the gfx straight-off without having to restart is there?
I tend to play the game in little spurts at varying times, rather than one long marathon session. It'd probably get pretty inconveniencing.

In Windows, a sufficiently advanced graphics driver configurator should let you disable/adjust the graphics card just for the target application. [I ended up doing this to work around a bizarre gamma correction issue with my old 1178x864 monitor.]

Yeah, I assumed that to be the case with my Radeon 9600se, but having looked over the options I'm coming up stumped.
I'm using the most recent omega drivers, with the old-style catalyst control tabs, since the slick new catalyst control contre interface doesn't work right on my pc (frameword issues, i think).