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Currently using 4.3.32 on Windows7 using a variety of primarily Windows guest systems. Was thinking on upgrading to version 5.0.15 but was wondering if the upgrade process is one way? In other words if I have problems with version 5 of VBox can I downgrade the VMs back to version 4.3.32 by reinstalling VBox and the Guest Plugins?

First of all, 5.0.15 is not an official released version, they're even numbered. You must have a TestBuild in mind. But that's not a problem. Neither is going from 5.0.x to 4.x, but that's my personal experience. Even if you have some features in the 5.x series that you change in one of your VMs (that didn't exist in the 4.x series), chances are your changes are reversible. For example, I installed an OSX 10.10 in VB 5.x and when I downgrade to 4.x it shows the VM as inaccessible, because the Guest type is unknown, which makes sense; you can't go back in time and change things.

If you want to be on the very safe side, a backup is always a good idea, especially in major version changes.

It has also been recommended that when jumping versions, 4.something to 5.something, or 5.something back to 4.something, you uninstall the present Virtualbox and reboot, then install the next version. Your guests will remain where they are, ready to be read by the new installation (if the guest OS is compatible, as Socratis said).

There is no need for doubt, just make backups of your VMs. There is really no excuse for not doing so.

scottgus1 wrote:It has also been recommended that when jumping versions, 4.something to 5.something, or 5.something back to 4.something, you uninstall the present Virtualbox and reboot, then install the next version. Your guests will remain where they are, ready to be read by the new installation (if the guest OS is compatible, as Socratis said).

My VMs are not in the default location due to space issues but rather on another partition. Will uninstalling version 4 require reconfiguring their location after version 5 is installed?

Theoretically no. Your default location is part of the preferences, which are honored between versions.