Success.
Windows 7 Home Premium 64bit SP1-U, no updates. HD 4350. No GUI Boot and Base Video ticked in MSCONFIG
Installed the CRT_Emudriver beta drivers as admin. MSVCR100.DLL error. Asks to enable test mode, tick yes. Rebooted.
Came up in 320x240 15khz.
Selected 640x480i in ArcadeOSD.
Unticked base video.
Rebooted.
Run GroovyMAME as Admin, all working perfectly.
Modeswitching is fast after the initial MAME load time (first run after boot).
Not touched any INI files except for VMMaker.ini. VMMaker is saying no compatible driver found (monitor is connected to \\.\DISPLAY1 according to the debug log) so it does nothing, but the modes built into the driver are all appearing in ArcadeOSD quite happily and GM is picking the right ones.
The driver version is 8.951.1.0, Calamity signed.