HDD-Light keeps blinking as if it's trying to install something, even when VB has been closed, and the PC is at rest

[maxwell's_silver_hammer]

I've installed VirtualBox, then Windows XP into VB, & then VBoxGuestAdditions.ISO into XP.

BUT now my HDD-Light keeps blinking as if it's trying to install something, even when VirtualBox has been closed, and the PC is at rest.

This is what I did.
On my W10 PC:
I installed VirtualBox & then Windows XP into the VB.
But VBoxGuestAdditions.ISO was not listed @ Device>Optical Drives
But it is listed in my PC @ C:\Program Files\Oracle\VirtualBox

So I mounted it manually, eg: Choose/Create a Disk image, etc.
Then I opened XP and selected: My Computer
Then I double-clicked on the 'Virtual Box Guest Additions drive' to install it.

It now appears to be installed, as: VirtualBox Guest Additions (D)
at: My Computer> Devices with Removable Storage

So: what's causing my problem?

Many thanks.

[multiOS]

Sorry, but your description sounds a bit confusing (to me). It suggests that you mounted the Guest Additions iso on the Host (Win10) system and installed it from there, which would be incorrect.

1. Please confirm where the Guest additions are installed by checking "Installed Apps" on the Host and also the XP Guest. If they have been installed on the Host system, then uninstall them and make sure they are installed in the XP Guest.
2. Also, make sure you unmount the Guest Additions iso after an installation has been completed - FYI: When VirtualBox is installed/upgraded the matching Guest Additions iso is automatically located in its default inallation location (where you found it) where any installed Virtual Machine will automatically look for it when the VirtualBox Manager or the correct Command Line commands are used to install them.
3. If the HD/SD indicator light continues blinking when a VM and ViirtulaBox Manager App have been shut, down the first thing to do is use Windows Task Manager to check what processes are causing the activity. It should be possible to see wherether there are any VirtualBox services that haven't terminated or, if the cause lies elsewhere, e.g. Windows File/Folder indexing/scanning.