video card help needed

I am currently having problems with my VC when I get into demanding graphics while gaming. I get that scary video card beep. I was to to use 'rivatuner' I haven't a clue where to begin I have "msi radeon 9550 \128 mb"(not the best but ok) it surpasses all the recommend requirments for the game (TRIBES VENGEANCE & TRIBES 2) I AM GETTING 'AVG 30 FPS AT 640X 860 RES. (FAIR) MY SYSTEM IS A CUSTOM BUILT ON A BUDGET( a decent system)
mobo asrock p4s55fxs+
cpu- 2.7 celeron w/ extreme cooling
op. system - windows xp pro
power supply- 420 wat
hard drive -80 gig
ram- 1 gig pc2700 ddr ram
3 extra fans9I don't think overheating is a problem
dvd/cdrw/floppy

any tips or ideas more than welcomed. I can afford $200 to $300 bucks for a kick'n video card how can I get the most out of mine. also how does the 9850 stack up against a radeon 9200 ati

 

5900xt goes for about 200$ (btw wrong forum)never heard of a video card "beep". Never heard of an 9850. You also mentioned 3 diff 3d cards; which one do you have now? and i doubt that getting a high end card will help you with a celeron.