Guest Additions in Longhorn

At first glance, it might seem impossible to run VirtualBox Guest Additions in any pre-reset builds. This is actually common misconception, and we can get a Longhorn VM running with a much better resolution following this simple workaround.

Note: the following tutorial only sets your resolution! It does NOT enable Aero effects!

Installing Guest Additions

Step 1: Insert the Guest Additions iso into your VM and right-click on the *.iso in Explorer, and click "Open".

Step 2. Right-click on "VBoxWindowsAdditions-x86" if you're using a 32-bit guest or "VBoxWindowsAddititona-amd64" if your guest is 64-bit.

Step 3. Click on "Other Properties", and select "compatibility".

Step 4. Check "Run this program in Compatibility Mode" and select Windows XP.

Step 5. Launch the VirtualBox installer and proceed with installation. Once done, click "finish" to reboot.

Step 6. After you've rebooted into your VM, open a Run box (Win+R) and enter in "C:\Program Files\VirtualBox Guest Additions" and click OK.

Step 7. Search for every *.exe in this folder (there aren't too many) and set them all in compatibility mode for Windows XP.

Step 8. Go to Start --> All Programs, right-click on the Startup folder and click "Open".

Step 9. Go to the Guest Additions folder and copy VBoxTray.exe

Step 10. Go back to the startup folder and paste a shortcut.

After rebooting, Longhorn's resolution will manually change! I hope this tutorial helped.