If you mash F8 on boot, do you get a recovery menu? There might be a recovery partition on there you could use to restore Vista.
The user manual suggests this, so it presumably was an option, but it doesn’t work now (or I can’t access it), just keeps going to the above screen. it says in the user guide there is a 1.5gb hidden partition on the hdd for system recovery.
I also have a HDD with Win XP on I took out of an old dead laptop, to access the music files. I’ve tried booting from that, but to no avail. it comes up with the Win XP start up screen, looks as tho things are going to happen, but then blobs out back to the above screen. I’ve no idea whether that would normally be expected to work anyway tbh?.
Even tho I own the Win Vista that came with it, there’s no obvious product key in all the bumf.