Occasional studder in the video display

Puter specs:
P4 3.5 800 fsb
intel chipset
ati 9600pro 256M
1 Gb dual layer ram
win xp pro
Been simming for about 3 yrs and finally got what I thought would be a good setup, and it is, most of the time. What I have is a really bad studder and once in a while a freeze momentarily of the screen. using the frame rates on screen shows in the 40 to 50 area most of the time and the graphics are fantastic, then all at once it just starts to studder really bad. can't seem to geta handle on it myself. Has anyone had this problem that might offer a solution? BIG Thanks in advance
JJ
P4 3.5 800 fsb
intel chipset
ati 9600pro 256M
1 Gb dual layer ram
win xp pro
Been simming for about 3 yrs and finally got what I thought would be a good setup, and it is, most of the time. What I have is a really bad studder and once in a while a freeze momentarily of the screen. using the frame rates on screen shows in the 40 to 50 area most of the time and the graphics are fantastic, then all at once it just starts to studder really bad. can't seem to geta handle on it myself. Has anyone had this problem that might offer a solution? BIG Thanks in advance
JJ