I had a similar issue with an old Kyro2 64mb (click here) and none of the drivers available (either Hercules or PowerVR reference) would provide good performance when image editing and creating 2D graphics.
My cure was to upgrade to an FX5200 and it was £45 well spent. In your case, you should check for a driver update and check that your graphics settings haven't altered recently before replacing the card.
BTW what chipset is it and what OS are you running? I can't say for sure whether your card is fast enough for your needs. Win XP may be a bit too much for really old cards like my Kyro2 if you have all the enhancements turned on.