I would like to check out Windows7 and install all of my developer programs on it just to test if everything works fine. In the mean time I want to continue my work on my Vista os. Is it possible, using Virtual PC, to install Windows7 and afterwards replacing my Vista installation with this Virtual PC Windows 7?
Take a look at using a bootable VHD. I have one with Windows 7 and use this as my "playground" for testing things like VS2010 Beta 2, Office 2010, etc. The VHD is a single file so it's portable and the performance hit for the virtualization is minimal.
Instead of running a Windows 7 VPC inside Virtual PC inside Vista, you are booting into a Windows 7 VPC - no Vista. works great for multi-booting. Once you're ready to move to Windows 7 as your primary OS, you can still use it in a VHD.
This link may help out... http://4sysops.com/archives/how-to-add-a-windows-7-vhd-to-vistas-boot-manager-menu/
In theory, yes. Back up the virtual image, then restore it to your hard drive.
In practice you may find issues with drivers, specifically video, as effectively you're moving a Windows image from one "computer" to another.
You'll also need to make sure that the Windows license comes over properly - best to not activate it while it's virtual.
If it were my box I'd probably want to do this to a fresh hard drive, so I can fall back to Vista if all goes wrong. So rather than virtualize, I'd just buy a new hard drive and use that for Windows 7 straight away.
Have you considered dual-booting?
Also: Windows 7 was designed to be compatible like Windows Vista, unlike how Vista was sometimes incompatible with XP. You probably shouldn't have any problems with compatibility.