Panman,
I have a simalar system...AMD 500 K-6, They are not the best processors for gaming as I've been told , something to do with the math processor.
First thing to do is buy as much ram as you can afford....It makes a Huge differance in your frame rate....256 megs at least. I picked up 128meg from Fry's for 30 bucks not long ago.
Next close every program you don't need to fly AH...I don't even run my anti-virus.
Make sure you have the lates drivers for your video card...You can download them online. Dang read your post again...AH is just not flyable on a onboard video.
You could pick-up a vodoo card for cheep now...they work the best with a k-6 board...don't do like I did and get a tnt2 card as they are not compatable (they will work but the vodoo will kick #$s)
I also set my own Virtual memory , Set the min at 150 and the max at 1.5 your ram ...For your machine 192mb x 1.5 = 288
Believe it or not I started at 4 frs....man did that suck....But now I'm running a solid 22 to 25...not great but flyable
You didn't say but any usb stick would help also.
Every one will tell you the best fix is to buy a new puter and make that one a boat anchor , but if your like me a 1000 bucks doesn't grow on trees.
Best of luck... Hope I could help Questions?
Salt