menotu, thanks for your reply.
could you pls. elaborate? i'm a bit thick with this matters...
Have a look in the folder .virtualbox/HardDisks (which is under your /home folders) you may need to select "Show Hidden Folders" in Dolphin
In that HardDisks folder you'll see a file with a .vdi
extension which will correspond to the name of your Virtualbox VM (or it will have the name you gave it it you specified a certain HDD name when you created your VM)
Anyway, that .vdi file is actually the Hard Disk of your VM, therefore its just a matter of copying that somewhere safe and re-using when required.
Think of it as if you've taken your ACTUAL REAL
hard disk out of your main PC for use in another PC.
So when you create a new VM you can point it to that hard disk and voila! it will boot to whatever OS you have installed on it.
I have half a dozen backup VDI's on another disk. Its like a "remaster" but in Virtualbox's VDI format.
If you need any clarification luikki, please just holler.