Exactly which WDDM driver did you get working with Windows 7? I'm using Win 7 Ultimate x64.http://www.matrox.com/graphics/en/support/drivers/
On the Matrox site, there doesn't seem to be any WDDM drivers that support the MMS series cards, only XDDM/WHQL. I tried the Vista x64 XDDM for MMS etc (2.09.00.158 SE U) and Vista x64 WDDM (3.01.00.230 WDDM M WHQL) for M-Series, neither worked.
Thanks in advance for your help.