It sounds to me as if VirtualBox is booting into the live desktop from the ISO file every time you start. Either you never installed the OS to the virtual machine, or there is an error in the boot order setting.
To check the boot order, start VirtualBox and, before starting the system you are trying to use, click the "Settings" button ( it looks like a yellow gear wheel). In Settings, open "System" and check the boot order. If the CD/DVD-ROM entry ids above the HARD DISK entry, the virtual machine will always boot from the ISO file and not from the OS installed on the virtual hard disk. If this is happening, every time you power down the virtual machine by any method, you will lose all installed apps and all work mot saved to an external drive.
The solution is quite simple. If you have not installed the OS to the VirtualBox virtual drive, run the installer and install the OS, making sure that after the installation is complete, the virtual machine is set to boot from the HARD DISK first (HARD DISK is above CD/DVD-ROM in the boot order diagram).
If the OS is installed, just correct the boot order.
If this is not a solution, post back here and we will try plan B.
Registered Linux User 483387