Mac address Change

Been trying to import my Parallel Desktop VM from Mac to Parallel workstation on Windows, and realize that some of the network card Mac address that I've predefine is not valid? looks like the first 3 digit of the Mac address seems to be lock. Is there a work around. Find it impractical why to lock the mac address in windows, but not in Mac Parallel Desktop?? Also, VMware doesn't have these limitation....

- ben