Yes you can. If moving it to another PC, just copy over the .vdi file and import it using the 'Virtual Disk Manager' under the 'File' menu . Then create a new VM with the same 'hardware' settings as the original and point it to an existing disk image (the one you just copied over).
If you want to run another instance on the same PC, you must 'clone' the image to create a new unique ID before you can import it using the disk manager. On windows OS, open a command prompt in the program folder and type;
vboxmanage clonevdi filename.vdi newfilename.vdi