Got better performance from parallels

Recently parallels has been running really badly on my MacBook Pro. I tried changing different options but nothing worked.I would start parallels, load a guest OS and the whole system would grind to a halt-- even if windows wasn't actually loading (if it had stopped on the boot screen).

I was suspicious of this, because parallels had always been runnning ok previously on the same system- I just hadn't used it for a while.

A couple of days ago I did the following:
•Imaged the startup disk to a DMG file.
•Restored the disk from the DMG file (via target disk mode).

For whatever reason, Parallels is now working properly again.