Symptoms
When playing games in Windows virtual machine running in your Mac, you may notice that Ctrl, Alt, Cmd, Shift and other modifier keys fail to work properly.
Resolution
To solve the issue, you need to edit the modifier keys handling settings in your virtual machine configuration. To do this, follow these steps:
Parallels Desktop 5 for Mac:
- Open the configuration of your virtual machine by choosing Virtual Machine > Configure from the menu. If you are working in Crystal or Full Screen, you need to switch to another view mode to be able to access the menu.
- Click the Options tab > Services and select Optimize modifier keys for games.
- Click OK to save the settings.

Parallels Desktop 6, 7 and 8 for Mac:
- Open the configuration of your virtual machine by choosing Virtual Machine > Configure from the menu, in Coherence > Alt+click the Parallels icon and choose Configure from the menu. If you are working in Full Screen, you need to switch to another view mode to be able to access the menu.
- Click the Options tab > Advanced and select Optimize modifier keys for games.

Once Optimize modifier keys for games is selected, Ctrl, Alt and other modifiers will work properly in games.
NOTE: The solution is valid for Parallels Desktop since version 5. It is not possible to backport it to prior versions neither to implement a workaround. To use the feature, please upgrade your Parallels Desktop to version 5 or later. You can find actual upgrade policy at:
www.parallels.com/products/desktop/
No
Yes