When I play DKG it starts lagging after about five minutes or so. Both sound and graphics. And it's a very heavy lag as well.

My computer is:

800 mhz
256 Mb RAM
8 Mb graphics card with 3D acc. (built-in on mother board)
win 98 SE
SB Audigy 2

The game is not a cd-rip, it's the low-price release from Dice.

Any suggestions on why it lags, and what to do? I've tried to kill all unnecessary background tasks, but that didn't help.

The lag is very annoying since it definately makes the game unplayable... :/

Save your current game, quit DK and start it anew. That lags should usually only happen in the first 5-6 levels. After that it happens only rarely. The lags come because the game doesn't have an automatic speed adjustment in the engine, and as it runs too fast, it comes with time to slowdowns instead. ;)

Aha. Thanks I'll try that! I'm only at lvl 4 at the moment so I hope you're right about the lag disappearing in higher levels. =)