Windows 7 is installed.
Native VHD boot is restricted to the following editions:
Windows 7 enterprise
Windows 7 ultimate
Windows server 2008 r2
Mkdir c:\vhd
Windows server 2008 R2, enterprise
copy D:\sources\install.wim c:\vhd\Windows2008r2.wim
Windows 7 Enterprise, 64bit
copy D:\sources\install.wim c:\vhd\Windows7Enterprise64.wim
Diskpart
create vdisk file=c:\vhd\Windows7.vhd maximum=25000 type=fixed
Select vdisk file=c:\vhd\Windows7.vhd
Attach vdisk
List disk
Select disk 3

Create partition primary
Select partition 1
Active
Format fs=ntfs quick
Assign
create vdisk file=c:\vhd\Windows2008R2.vhd maximum=25000 type=fixed
select vdisk file=c:\vhd\Windows2008R2.vhd
attach vdisk
list disk

Create partition primary
Select partition 1
Active
Format fs=ntfs quick
Assign

Assuming the imagex.exe utility is copied into C:\
C:\Imagex /info c:\vhd\Windows7Enterprise64.wim

C:\Imagex /apply c:\vhd\Windows7Enterprise64.wim /check 1 H:\
C:\Imagex /info c:\vhd\Windows2008R2.wim

C:\Imagex /apply c:\vhd\Windows7-32bit.wim /check 3 J:\
Diskpart
Select vdisk file=c:\vhd\Windows7.vhd
Detach vdisk
Select vdisk file=c:\vhd\Windows2008R2.vhd
Detach vdisk
DISKPART> exit
Leaving DiskPart...
Create boot
entries
bcdedit /copy {current} /d "Windows 7 Enterprise 64bit"
The entry was successfully copied
to {08408e64-86cc-11de-9489-d4df34687acd}.
bcdedit /set
{08408e64-86cc-11de-9489-d4df34687acd} device vhd=[c:]\vhd\Windows7.vhd
bcdedit /set
{08408e64-86cc-11de-9489-d4df34687acd} osdevice vhd=[c:]\vhd\Windows7.vhd
bcdedit /set
{08408e64-86cc-11de-9489-d4df34687acd} detecthal on
bcdedit /set {08408e64-86cc-11de-9489-d4df34687acd}
description "Windows 7 Enterprise 64 bit"
bcdedit /copy {current} /d "Windows 2008 Enterprise R2"
The entry was
successfully copied to
{08408e65-86cc-11de-9489-d4df34687acd}.
bcdedit /set
{08408e65-86cc-11de-9489-d4df34687acd} device vhd=[c:]\vhd\Windows2008R2.vhd
bcdedit /set
{08408e65-86cc-11de-9489-d4df34687acd} osdevice vhd=[c:]\vhd\Windows2008R2.vhd
bcdedit /set
{08408e65-86cc-11de-9489-d4df34687acd} detecthal on

A test
I move the vhd files to E drive and modify the BCD store accordingly.
bcdedit /set
{08408e65-86cc-11de-9489-d4df34687acd} device vhd=[E:]\vhd\Windows2008R2.vhd
bcdedit /set
{08408e65-86cc-11de-9489-d4df34687acd} osdevice vhd=[E:]\vhd\Windows2008R2.vhd
it works.
If not all menu items show when computer starts, press down/up arrow key for a selection.