Choppy performance,cmos beep

hey all, i'm having trouble with performance in bf2. I have played for the last couple of years with the same hardware, with no problems. I'll be in a game and it starts to stutter or lag , and sometimes the sound will make a screech and at the same time sometimes i hear the actual cpu box beep once, seems to freeze for a split second and away i go again for a while staying in game like nothing happened. I have tried vid drivers ,sound drivers blew out the case quickly, checked vid temp i think it was 40-50c ,never checked cpu temp(guess i would have to shut down comp and reboot into bios to see this?). any thoughts ? does the single beep mean anything ,bad memory, etc?

My specs (I know its old, waiting for bf3)

a64 3500
2 megs ddr (1 m 333/1 m 400 )
ati sapphire 1950 pro agp
gigabyte ga k8u-939 mb
250 gig hd
dvd burn
cd burn
floppy
500 antec psu
windows xp fully updated
avg virus scanned
defragged