From my experience, when using a non-supported graphics card in opengl mode, sometimes it works 100%. But usually, there is some problem - highlighting, line drawing, artifacting, any number of potential graphics problems. At that point, your option is to live with it, use software rendering mode (win32_gdi or something like that in your preferences) or use a different computer.
Of course, when using a laptop, your choices are much more limited - at least on desktops, the low-end Quadro cards can now be procured for $120 (I use the Quadro FX 370 with dual heads and ProE WF4/M70 without any issues and with great speed, even with assemblies up to 700 parts or so).
But, as I mentioned, sometimes a gamer card will work perfectly. I have another workstation which is Vista64 (quad core, 8mb ram) with Nvidia GeForce 9800GT. This is also running ProE WF4 M070. It has no issues and is the fastest proe workstation I've ever used and saw no need to change the video card based on our tests.
I hope your configuration works out - good luck.