Originally Posted by larryhaja
Not sure what you mean by "seamless" mode.
Seamless mode for a VirtualBox virtual machine combines the desktop of the VM with the desktop of the host OS. The taskbar (or panel) of the VM is positioned just above the host OS taskbar. Windows for the VM appear as if they are normal windows on the host OS desktop. The windows for the VM still behave like those for the guest OS and have the same window decorations. This also seems to assume rectangular windows and I've had some problems with non-rectangular windows.
Seamless mode works better with a Windows host OS but it still works adequately on a Linux host OS.
A recent feature added to VirtualBox displays a small mini toolbar for each VM at the top or bottom of the host OS desktop. That allows access to features such as mounting discs or sharing folders.
I use seamless mode to do Windows XP software development in an XP virtual machine running on top of Windows Vista. I'm considering using Linux as my host OS instead of Vista.
You can easily get into and out of Seamless mode by pressing the host key at the same time as "L". The host key is usually the right-hand "Ctrl" key.