I've seen that for years as video cards age and then become heat sensitive.
Let's try doing our yearly maintenance you can see at this link -> http://reviews.cnet.com/4520-11319_7-6240575-1.html
Would appreciate some advice, my aging computer has developed an irritating problem: what in the old days of early TV was known as "sound on vision" , in other words occasionally the sound would distort and the vision freeze or pixilate. My Fujitsu Siemens 2.4ghz P4 has the sound system built into the mother board (AC97). I do have a new sound card and am considering installing this and shutting down the in built sound. Question,is this likely to overcome the problem? (can't afford to purchase new computer at moment!!) Thanks Dave