Parallels 8 question

Parallels works on OSX and creates Files on the OSX FileSystem that contains the VM and all the VM Data.
You can also run the WIndows Apps directly in the finder, without "showing" windows.

If you use Bootcamp just for Visio like tasks, drop it and go with Parallels or VMWare.

 

Parallels can use your bootcamp partition to run Windows under OS X. Or you can delete your bootcamp space and reclaim that for the Mac. If not using bootcamp partition, Parallels creates a virtual HD (a big file) in which to run Windows. The virtual HD does use a bunch of physical space but the nice thing is that you can expand and compress the virtual HD as needed.

Parallels can also access the Mac HD directly so that you can store your data files directly on your normal file system. You have choices to keep the Windows virtual machine very isolated from the Mac or to have nearly seamless integration.

I've opted for limited integration as I do only a few things in Windows. I access my Mac HD from Windows via a virtual network share.

Note that if you reactivate Windows under Parallels, Microsoft might reject that as an attempt to register the license on more than one machine. This can be resolved with a phone call to support.