Windows 7 installation creates a 100-300 MB partition to easily enable bitlocker with out repartitioning the disk in future, but in cases of virtualization there is no need for bitlocker and this volume can be safely recovered by following steps.
- Bcdboot c:\windows /s c: from command prompt with admin token.
- Make c: active using diskpart or disk management.
- Delete the 100-300 volume using disk management.
- Expand C:\ to utilize the unallocated space.
This can also be prevented in first place by using the following variable in Customsettings.ini (MDT)
DoNotCreateExtraPartition = YES