Running a specific edition of visual Studio (Insta

I have Visual studio 2012 Ultimate and Professional installed on my computer. By default Windows opens up Ultimate, is there a way to specify which version I want to open?

This applies to all versions and editions of Visual Studio (apart from the express editions).

Visual Studio installations of the same version (2010, 2012, 2013 etc) use a common base location and each edition (Shell, Community, Professional, Test Professional, Premium, Ultimate, Enterprise) you install on top of Professional/Community basically extends the Visual Studio installation to give an integrated environment.

It's how SQL Server Data Tools, BizTalk and other extensions are able to provide a stand-alone editor (Integrated Shell) on a system that has no Visual Studio installation, but it also means that it will just "extend" your community edition.

Alternative options for you, if you want to work only with the license you have available for personal use are:

Use Windows' boot to VHD feature, allowing you to multi-boot into a Virtual machine, either for personal or work usage. This uses additional space, but also gives very good separation. If you're really good with dism, you may be able to create a base image for your personal and your work environment to save space.
Boot from a secondary harddrive using the windows Boot Manager.
Use Hyper-V (or VMware or Virtual Box) on your Windows installation and create a virtual machine for either work or personal use of Visual Studio (or create two Virtual machines).
Create a Windows-to-go installation on a USB drive and boot from that.
Host one of your development environments in the cloud, use the Visual Studio images on Azure for example.

Or use your work license for your personal use and try not to use the ultimate features ;). as far as licensing is concerned, MSDN licenses are assigned to an individual, meaning you are licensed to use that instance of Visual Studio. As Lasse says, it looks like it may be a company policy issue instead of a Microsoft licensing issue. Another thing to keep in mid may be Intellectual Property Rights, where in some countries the usage of a license granted by an organisation gives the organisation claim to the IP.

In case of Retail Visual Studio licenses (Visual Studio Professional Retail), the license isn't granted to you as a person, but to the machine.

Other licenses (SPLA, Volume License, VSO professional) muddy the water even further.

In order to protect yourself it's best to create a clear separation between the different licenses by creating a virtual machine.

With multiple editions on the same machine the following applies (this applies for all editions higher than the express editions):

Visual Studio shows the splash screen of the highest edition you have installed on your machine.
If you need to remove Ultimate for some reason, you need to uninstall Visual Studio Ultimate from your machine and then repair Professional. After repairing a Visual Studio edition, you will need to re-apply the latest update pack.
If you need to selectively run one or the other (due to license constraints for example), you'll need to create different boot images or run them inside a Virtual machine.
If you need the features of one or the other, it doesn't matter which one you start. All features of all editions you install will be available on the same machine.