Since you are using Windows 7 Home Premium you will not be able to download the newer version of Windows Virtual PC (You need to have Windows 7 Pro or higher)
I also found the older version, Download details: Virtual PC 2007
This version might or might not work I have not really tried it out on Windows 7.. It says it works for Vista so I am guessing this might work for Windows 7..
Do you have to use Virtual PC? there are others like VirtualBox
which I found easier and I personally found it better than Windows Virtual PC... and it will work for Windows 7 Home Premium..
Hope this Helps..