Windows 7 and Disk2VHD
limneos... the VHD Resizer was what I needed as the final piece to a bigger puzzle. Slightly different situation than the post above. Maybe this will help others as a key to upgrading to Windows 7 while still holding onto your current Windows XP PC as a Virtual PC during the transition:
On your XP desktop run Disk2VHD to create a virtual hard drive of your current PC.
Disk2vhd.
Microsoft notes one caveat that the VHD cannot be sourced from a disk larger than 127GB. We found that you can use it with a larger disk with a bit of tweaking and with one further caveat. You cannot have more than 100GB used of a larger disk. In my case, the disk was 232GB but was only using 55GB. So I ran the Disk2VHD process on my disk and shuttled it off my PC to an external drive.
I then formatted my PC and installed Windows 7 64bit.
I then followed the process here to install XP Mode for Windows 7.
Please note prerequisites and versions of Windows 7 that support XP Mode.
Download Windows XP Mode
One thing that Disk2VHD doesn't tell you... if you want to launch this VHD as a Virtual PC, you have to manually replace the hal.dll and halacpi.dll from your source Windows XP installation. Please use the ones from the correct service pack.
To do this, go to Disk Management and attach VHD.
You can then modify the contents of the VHD by placing these files in the system root (c:\Windows\System32 by default). Before you Dettach, you should use Disk Manager to Shrink the partition as much as possible. Remember to Dettach and resave the VHD file before attempting to mount the Virtual PC.
I then ran VHDResizer on this shrunken partition to create a smaller VHD from my bigger disk. I was then able to create a Virtual PC with this VHD of my old Windows XP image.
One last Caveat: To get your device drivers fixed, you will need to run the Integration Services.
If only Virtual PC had a tool as easy as P2V from VMWare to work through this...