Unable to mount VirtualBox Guest Additions as a guest (Win7 host)

Question

I keep getting this error dialog with an Unable to mount error E_FAIL ( 0x80004005 ) when I try to mount Guest Additions:

I tried the Force Unmount, but that just closes the dialog with no action taken. If I then reattempt to mount Guest Additions, I just get this same dialog box again. Any help would be greatly appreciated!

Answer 1

Finally, I figured it out. Here is how you get arount this. First, load Disk Utility and manually eject the disk in the CDROM, by clicking on the Eject button, after selecting the CDROM device. Then try to remount Guest Additions using the key combination Host + D and voila, Guest Additions should mount successfully.