More on Boot from VHD - Disk2vhd

A little while ago I wrote about how impressed I was with boot from VHD in Windows 7. This morning I was trying to convince Mike that using this technique with a base Windows 7 VHD and differencing disks would be a great way to get VS2010 Beta1 and Beta2 (when it arrives) installed on his machine.

He wanted to know if he could just create a VHD from his existing install ie snapshot his native Windows 7 installation to VHD. That had me foxed although we talked about whether or not Windows Backup might be a possibility.

Then, as if by magic, I came across Disk2vhd which does exactly that – “create virtual hard disks copies of the physical disks that are attached … Another potential use is to allow you to move a physical installation of Windows 7 to a “boot from VHD” configuration.” Bingo!

Direct download link is here.

Technorati Tags: vhd,windows 7,boot

Comments

• Anonymous
  October 13, 2009
  Mike, a word of caution about the Disk2Vhd utility you mentioned. On the download page, it says that you can't snapshot a physical machine and then use it to boot from VHD on the same machine... Note: do not attach to VHDs on the same system on which you created them if you plan on booting from them. If you do so, Windows will assign the VHD a new disk signature to avoid a collision with the signature of the VHD’s source disk. Windows references disks in the boot configuration database (BCD) by disk signature, so when that happens Windows booted in a VM will fail to locate the boot disk. If you, or the SysInternals guys know of a workaround for this, let me know!

• Anonymous
  October 13, 2009
  Hi James. Yes, MikeT, Barry Dorrans and I had a discussion about this as it is ambiguous. Barry interpreted it as you have whereas Mike and I interpret it differently :). Our interpretation is you shouldn't create a VHD from a specific Windows install and then attach it to that system if you later want to boot from it. (There's an option in Windows7 to attach a VHD as if it were just another drive). It's okay to boot it on the same machine but if you attach it, Windows changes this disk signature to avoid a conflict. The boot manager then has a different signature stored than the one your VHD now has so it wont be able to find it. On the Disk2Vhd page I think there is an image of a VHD system running on the same system it was created on which seems to suggest our interpretation is correct but I haven't tested it to confirm. All the best Mike

• Anonymous
  October 13, 2009
  Mike, whilst the screen shot on the download page shows a VHD running on the same machine it was created on, this was running inside Virtual PC. I think the notes on the download page warns against trying to run the VHD as a boot device...if I interpret it correctly. Has MikeT had a go at this yet? It sounds like what he wants to do is what I want to do...

• Anonymous
  October 13, 2009
  Hi James Hmm - you're right. I should have looked at it more closely. MikeT has a problem with Disk2vhd erroring on his machine and was in communication with Bryce about it but I don't think it's resolved. I created a VHD successfully but subsequently deleted it without trying to boot from it (as I already have a bootable Win7 VHD). I'll find out for you one way or the other... Mike

• Anonymous
  October 14, 2009
  The comment has been removed

• Anonymous
  October 15, 2009
  Mike, thanks for getting back to me. I'm not going to risk it, I'll stick with a physical Win7 system for now and look into the VHD option at some future point, perhaps if I ever need to rebuild the machine.

• Anonymous
  October 15, 2009
  I still haven't given up. I'll let you know if I get it working. Of course this is just about Disk2vhd VHDs - I'd definitely recommend native boot from VHD as a great option. You just can't use Disk2vhd as a shortcut to creating the VHD at this stage. Mike