Because it is lacking a math processor

The AMD's are designed for running fast application for a fraction of the price of a Intel chip.

Please don't double post. Use the edit button - Daniweb Mods

It should run them fine, provided you don't have some sub-1Ghz model (then you're just lacking general grunt - it would be a similar story for any other CPU in that range). STP72, maths co-processors being sold separately went out in the days of the 486!

What computer do you have exactly? Specifications please!

Also dont forget that it is not only the cpu that is important for games. You need a good amount of RAM, I wouldnt recommend less than 512mb but the most important thing is the Video Card. Like coconut said, you should tell us what your PC has as hardware (video card, CPU, RAM, and motherboard).

Well i've got a 2ghz celeron (128kb cache). An ASRock M266A motherboard
with socket 478. 1x 265mb memory module. 40 gb i think 7200 rpm harddisk (ata 133 i've got no idea what this means. A AOpen MX440 Geforce 4 with 64 mb's of DDR Ram
and a 250 mhz GPU.(The video card provides AGP 8x but my motherboard only
supports 4x).

And thats about it. But the strange thing is GTA 3 and Vice City work fine.
Only in high detail and high resolutions they start swapping and that sort of thing.

2 things you could add to that system to make it a bit better Pim. A better display card for starters. Another 256Mb of RAM to follow up. That should improve your gaming quite a bit. It won't make your system a great one for gaming, but it can certainly be better.

Yep the video card is extremely far from being acceptable for gaming. Horrible!!! For less than 50$ you could get a better card than this.

Well i've just formatted my harddisk and installed ME because win98 was complaining quite a bit about the wireless internet connection..
so guess thats not it. But i found that Command and Conquer:Generals didn't
work very well either.

maybe buy new motherboard+processor? (AMD)

Well the minimum video card required for UT 2003 needs at least 16mb's of ram so with 64 i'd expect acceptable performance with 4x that...

Command and Conquer:Generals doesnt run very well with a radeon 9000 128mb so there is no surprise the MX440 wont run it well. Dont expect too much out of your video card. If you think of getting an upgrade, tell us your budget and what you would change, if you can build it yourself that is. You could get a reasonably capable system by purchasing a barebone kit and video card both for about 500$us (a barebone has the case, power supply, motherboard, CPU, RAM, sometimes keyboard and mouse. You then add you own hard drive, cd roms etc).

edit:

:!: You cant base a card performance just on the RAM. It has multiple other things to take in consideration.