Updating Guest Additions in Windows 7 Breaks It

[Kirsle]

This has happened to me twice now, and here are the details from the most recent time.

1. Boot an old-ish Windows 7 VM that has Guest Additions 4.3.14 installed
2. Balloon from the tray tells me to update to Guest Additions 4.3.20 (also, the current version of VirtualBox)
3. I mount the Guest Additions ISO and go through the setup process
4. The experimental 3D option is *NOT* checked. I simply install the base additions.
5. On a reboot, the Windows loading animation plays and then I'm stuck at a blank, black screen. The Windows cursor appears if I mouse over the VM's window area but nothing else happens.

I can boot the Windows VM into Safe Mode and uninstall the Guest Additions, and then it can boot normally to the desktop. Re-install the Guest Additions, same symptoms as #5 above.

The last time this happened I just scrapped the whole VM and did a fresh Windows 7 reinstall from DVD image, installed most up-to-date Guest Additions, no problems. It only happens when I'm upgrading an existing VM to the latest additions.

* Host: Fedora 21 (x86_64)
* Guest: Windows 7 Ultimate x86_64

I'll keep the VM around this time so I can see if there's any solution to this aside from "delete and re-install from scratch".

[loukingjr]

You don't want to install the guest additions in Windows 7 in safe mode. If you are updating, you should also install the matching extension pack in your host if you have one installed.