When starting WinXP in Parallels Desktop, I get the following "error message": "The amount of video memory is too low. The 3D acceleration support is enabled for this virtual machine, but the amount of video memory allocated to it is lower than 256MB. You are highly recommended to increase the amount of video memory for optimal 3D performance." From what I can see, it's not possible to turn off 3D aceleration support or to increase the amount of video memory -- both are grayed out. FWIW, I'm not aware of any performance problems with the present settings. Any thoughts or suggestions would be appreciated.
Disable Windows autostarting under configuration and disable auto shutdown of parallels as well, when you close Windows. When you shut down Windows you can access the greyed out configuration items such as memory, video memory and the number of processors if you have more than 1.