I assume F2 gets you into the Bios, what does F12 get you? Don’t let it change anything until you know what it’s changing.
Did it come with Vista? If so, did it come with an O/S disk or is it on a partition on the hard drive and you were supposed to burn it onto CDs or a DVD?
My Sony laptop had Vista as well on a separate partition you were supposed to burn your own copy but I seem to recall there’s a way to boot into that.
Have you backed up your data? If you go through a restore using Toshiba’s utilities, assuming it has them, it’s possible it will format your disk losing all your data.
If it came with a disc, I can’t find it.