Hey guys, I just noticed that when I upgraded to the latest version of VirtualBox on Vista 32bit SP1 the installation completes but then the actual program does not install, the previous installed version is deleted, as are all of my VDIs and when I now try to install again, it claims installation is complete but doesn't actually install at all.
Somewhat confused. Your profile says you are using a different configuration. Anyway you need to reboot to see these changes. Other things that could cause this is the Vista UAC. Right click the install program and then left click on run as admin.
As you can see I am using Vista as host and do not see these issues. Of course I have not turned off UAC and let Vista do it's thing. That may be where you are having a problem. Windows expects to be run as it ships for the most part. Try turning it back on and then try the install by right clicking and left click on run as admin. Remember that run as admin is not the same thing as you having admin permission. The actual admin has GOD rights and it is not the exact same thing and being in the admin group. See if this helps and if not then we can proceed further.
Another thing that may be causing you problems is that the previous install was not loaded correctly. If that is the case you can also try the following: re-install the previous version and select repair. When it is done DO NOT reboot. Run the previous install again and tell it to uninstall. Still DO NOT reboot. Now install the new version and when complete this time reboot and see it it fixes your problem.
Read this and although it does not seem so it may apply to you. http://www.virtualbox.org/ticket/3701#comment:6 Try this and if it does not help you will need to submit a ticket to bugtracker. You will need to setup an account there as it is on a different system.