http://blogs.msdn.com/b/virtual_pc_guy/archive/2009/08/19/running-virtual-pc-2007-on-windows-7.aspx
If you get the "This program is blocked due to compatibility issues" on the Windows 7 RTM then you need to do the following:
1) Have to remove Virtual PC from the
- Control Panel > Programs and Features
- Then click on the "Turn Windows features on or off" link on the left
2) Uncheck "Windows Virtual PC". After this you will need to reboot.
3) Then you can install the new Virtual PC 2007 SP1
Note: you cannot just install the Virtual PC 2007 SP1 without disabling the Windows 7 built-in Virtual PC feature.
Virtual pc 2007 can be installed here: