Determine if your system is a virtual machine (Hyper-V/VS/VPC) inside Vista or Server 2008

It is as easy as checking HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SystemInformation\SystemProductName to see if it contains the string Virtual. There are also some other system call tricks, like revealing if the OS is a Server Core, located here.

It looks like, if you wanted to, you could gather most of the information with PowerShell too. It looks pretty straightforward.