How It Works
All of these features work similarly. You start up your virtual machine, launch the programs you want to use, and then enable “Seamless Mode” or “Unity Mode.” The guest operating system’s desktop and the virtual machine window will vanish, leaving the guest operating system’s windows on your desktop. They’ll appear to be running as if they were running on your host operating system, but the virtual machine is still running in the background. The programs are still sandboxed so they won’t have access to your host operating system’s files — they just appear to be running on the host operating system.
These tricks work whether you’re using Windows, Linux, or Mac. You can seamlessly run Windows programs on your Linux desktop or run Linux software on a Windows one.
Using VirtualBox’s Seamless Mode
Note that VirtualBox only allows you to use this feature with Windows, Linux, and Solaris guests. If you manage to get Mac OS X running in a VirtualBox virtual machine or you’re using a niche operating system like Haiku, you won’t be able to use this feature.
Before using this feature, you must install the VirtualBox Guest Additions software package inside the guest virtual machine you want to do this with. If you haven’t done this already, boot up the virtual machine, click the Devices menu, and select Install guest additions. You’ll be prompted to install the software.
To use this feature, press the “Host key” — normally the right Ctrl key, but it’s displayed at the bottom-right corner of the virtual machine window — and L at the same time. You can also just click the View menu and select Switch to Seamless Mode.
VirtualBox will hide the guest operating system’s desktop background, making it seem as if the guest operating system’s programs are running on the host operating system’s desktop. However, the running applications won’t appear on your operating system’s standard taskbar.
To exit seamless mode, just press the host key and L again. You’ll also find a VirtualBox menu above your taskbar, which you can hover over to view. Click View and select Switch to Seamless Mode again to disable seamless mode.
Using VMware’s Unity Mode
VMware has a similar feature named Unity mode. It’s available on the free VMware Player as well as VMware Workstation and VMware’s other paid applications. As with VirtualBox, VMware’s Unity Mode works for both Windows and Linux guest machines.
Like VirtualBox’s seamless mode, VMware’s Unity Mode requires VMware’s own software package to be installed inside the guest virtual machine, Before trying this, ensure that VMware Tools is installed in the guest virtual machine. You can do this by selecting the Install VMware Tools option in the VMware program’s menu.
To enter Unity Mode, click the Unity option in the VMware program’s menu.
Unlike with VirtualBox, programs running in the virtual machine will appear on your taskbar as if they were running in your host operating system. You will have access to a Start or Applications menu that allows you to launch applications in the virtual machine.
To display the Start menu on a Windows host, point to the Start button. To display the Applications menu on a Linux host, point to the upper-left corner of the screen. Select Exit Unity in this menu to disable Unity mode.
VMware also allows you to create shortcuts directly to applications inside the virtual machine. Just right-click an application in the menu and select Create Shortcut on Desktop. You’ll get a desktop shortcut on your host operating system, which will launch the program running in the virtual machine when you launch it.
Windows XP Mode
Windows 7’s Windows XP Mode actually functions in the same way, running a Windows XP virtual machine in Virtual PC in the background. Windows then displays the programs you want to run on your standard desktop, integrating them with your Windows 7 operating system.
Windows XP mode is no longer present in Windows 8, likely because Microsoft will soon stop supporting Windows XP, but you can use Seamless Mode or Unity Mode to get a similar Windows XP mode-like feature on Windows 8, if you like.
If you’re using Parallels on a Mac, you can select the Enter Coherence option from the View menu to display a virtual machine’s windows in the same way.