Biologic, I play DW on my sony vaio PCG-FR315B (no desktop where I live now,

). It has a Radeon IGP 345 that (this is funny) isn't supported from ATI.
With Sony stock drivers I have not managed to play games newer than about 2 year. I solved it using at first a modified drivers set (Omega

) and then Ati stock Catalyst modded (dhmodtool). Now I can play DW without problems (but the water isn't great

. And I use 32 or 64 Mb of shared memory.
So my suggestions are:
1) Look for new or modded drivers for your laptop.
2) Play with the properties of your video card. I've been surprised from the cut on artefacts it can do.