After resizing a virtual disk that Windows Server 2008 was based on I got the following error:

"Windows failed to start. A recent hardware or software change might be the cause."

File: \Windows\system32\winload.exe

Status: 0xc0000225

Info: The selected entry could not be loaded because the  application is missing or corrupt.

To fix this boot from the Windows 2008 DVD (The correct architecture based on the installed version 32/64-Bit)

Set the correct Language. Click Next.

Click "Repair your computer".

Then click "Command Prompt".

Run "bcdedit /enum" to list all the Windows Boot Manager entries. Take note the device and osdevice is set to unknown!

Run the following (modifying where needed) to set the correct device partitions.

bcdedit /set {bootmgr} device partition=C:
bcdedit /set {default} device partition=C:
bcdedit /set {default} osdevice partition=C:

Finally relist the entries to check they are correct.
bcdedit /enum

Type "exit" and reboot the server. If you set the correct partition it should now boot correctly.