The virtual machines in parallels are huge and will quickly eat up your valuable Time Machine space. These steps will prevent parallels from backing up your virtual machines to your Time Machine drive.
Virtual Machines take up a ton of space. My generic Windows 7 install takes 10 gigs of space. As soon as you build a virtual machine, Time Machine backup will gladly start mirroring to your backup drive.
If you are like me and do not keep any essential information in your virtual installations and drives, then there is no reason to back them up.
Here is how to prevent Parallels from backing up the virtual machines:
1. Load the Virtual Machine
2. From the Virtual Machine menu click Configure or click the Configure icon as circled below:
3. Select the Genera tab
4. Check No not back up with Time Machine
5. Select OK