VMware Workstation & Hyper V
When developing applications for Windows phone, Microsoft uses Windows Hyper V feature to run the Windows phone emulator. It wouldn't be a problem unless you have VMware workstation installed in your computer with a bunch of Virtual machines.
After installing both in the same computer, VMware won’t run as long as Hyper V has a role in the computer. Hyper V role needs to be off for VMware to run. The only way you can overcome this problem is disabling Hyper V but if you develop apps for Windows phone, its not really an option because you would be needing them both.
The solution I found for this problem was, temporary disabling the Hyper V engine until its needed again and the fastest way to do that is the Command prompt.
First open Hyper V manager and STOP the service.
Second in an elevated command prompt, enter following
bcdedit /set hypervisorlaunchtype off
When you want to enable it again
In an elevated command prompt, enter following
bcdedit /set hypervisorlaunchtype auto