Computer screen is fiilled with columns of video snow (kind of ala the Matrix).?

Happens within 5 minutes of turning on, gets progressively worse, cannot read, or MMO (haven't Lotro'd in over a year!, or anything, really). Any idea what causes this? It's an 11 year old computer, so not going to put any money into it. But if it's something that I could fix....Windows XP home, Radeon 9800 video card....could it be as easy as a video card update? I seem to remember having problems last time I did a video card update...Don't know for sure, kind of computer stoopid here...