upgrading & deleting old versions Bad Idea

I installed the ver. 6 upgrade then noticed a folder from Parallels2. So I trashed that.
Then got a Trash message (am using OS 10.5.8) of all these ancillary files for Parallels, and should they be trashed too? I clicked OK.
Then tried to start Parallels Desktop Mac 6, and got message that the virtual machine is not available.
Where is it? Can it be found? Did I naively put it in the trash?

 

Actually I had trashed but not deleted. So I carefully picked out what I thought were key, and put them back into the Parallels folder (the hdd image, the xp virtual machine) and it actually worked. No files lost.
Just time. So yes, use Uninstallers, not the too easy Trash option.