I have a Ubuntu 15.04 Dual booted with a Windows 7 installation so that I can play GTA5, but it is annoying switching back to Ubuntu for things like, virtualbox, Genymotion, etc. What I am asking is if there is a way to turn my Windows installation into a virtual machine on my Ubuntu Installation. Note that Ubuntu and Windows are installed on different disks, so nothing can be run with wine
You can do this with virtualbox if you set up the VM with no virtual HDD, and instead, give it the disk with the windows install as the virtual SATA 0 port. It should boot just fine, maybe have to go through some driver installs, but it should all come out in the wash.
Why you would want to do this in a VM is beyond me, unless you have servers running in Ubuntu. Why not just boot into Windows?
Also, make sure you allocate enough RAM for the VM. You can always tone down Windows 7 to make it less resource intensive. I have successfully gotten Windows 7 running on a 880MHz single core CPU with 192 Mb of RAM. It runs at a decent speed for things like dedicated servers (e.g. Star Wars Battlefront or Star Wars Jedi Knight Jedi Academy)