Does the upgrading from Parallels Desktop (for Mac) 5 to 6 means reinstall Windows? I have Parallels Desktop 5 for Mac. Does the upgrade to Parallels Desktop 6 means that I have to reinstall Windows 7 and all the other programs?
No, your Windows VM and all the programs installed on it are stored on a virtual hard drive file. Upgrading Parallels won't affect the VM.