If you’ve run into an issue where you are trying to create a Parallels VM but the installation process is stuck on the grey startup screen with the Apple logo then chances are its down to the VM System Settings
All you need to do to remedy this is shut down the machine (Click the power icon in the bottom left and choose Shut Down)
Once it’s shut down you then click on the cog icon in the bottom right to get to the Config options and set them as follows
On the General tab change the CPUs: to 2
On the Hardware tab, click on the Video option, then increase the Video Memory to 512MB
and thats it
Restart the installation process and you should now find that Mountain Lion installs as you’d expect
If you are running one of the VMWare products, such as VM Fusion on the Mac, then you may have run into an error similar to this
“Operation on file “/Virtual Machines.localized/VIRTUALMACHINENAME.vmwarevm/VIRTUALMACHINENAME-s012.vmdk”failed.
If the file resides on a remote file system, please make sure your network connection and server where this disk resides are functioning properly.
If the file resides on removable media, reattach the media.
Choose Retry to attempt the operation again.
Choose Abort to terminate this session.
Choose Continue to forward the error to the guest operating system”
Now this error is one of the most unhelpful error messages, as its completely misleading, the error is caused by not enough RAM being made available by the system, so the simple solution is to reboot, quitting all open applications, and freeing up more system memory.
To prevent this happening again in future try limiting the Virtual Machines RAM allocation to under 3GB, on machines with 8GB+ this should be fine.
Also, make sure that Spotlight is not trying to index your VM, as this may also lead to this issue
You can stop this by opening System Preferences, then click on Spotlight, then click on the Privacy tab, click the + button at the bottom and add the Virtual Machines folder, this is normally located at /Users/USERNAME/Documents/Virtual Machines