Hello,
Have you checked all Parallels settings? In particular RAM allocated to the virtual machine, and also the VideoRAM of the virtual Graphic card?
If you have installed your W7 on a Bootcamp partition, as a test, you should run ACAD on W7 booted directly on the Mac and not via Parallels, by doing so, you may validate ACAD installation or verify you still have performance issues or not? If not, then your perfromance issues may come from teh Parallels settings/installation?
Jose Rael
Autodesk Product Support