Problem
When upgrading to a newer version of VirtualBox on Windows there was an issue with installing an updated version of the VirtualBox extension pack. The Following error would appear.
Failed to install the Extension Pack
The installer failed with exist code 1: VBoxExtPackHelperApp.exe:error: Failed to rename the extension pack directory: VERR_ALREADY_EXISTS
rcExit=1
Result Code: E_FAIL (0x80004005)
Component: ExtPackManager
Interface: IExtPackManager {3295e6ce-b051-47b2-9514-2c588bfe7554}
Solution
To resolve this problem delete the following directory and try to install the extention pack again.
C:\Program Files\Oracle\VirtualBox\ExtensionPacks\Oracle_VM_VirtualBox_Extension_Pack-_-uninst
This worked for me first time. However if this doesn’t work there are a few more suggestions on the following forum post where I found this solution.