Thanks all, for the replies.
Yea, after App301 posted his bead designer, it occurred to me the MS Paint is a sensible starting point.
Mouser, Thanks very much for the offer! I don't think it'll work though, on Amazon there's a review that suggests it's not Vista-compatible. Also, I'm hoping to upgrade to Windows 10 at some point.
Miles, I will definitely check out that site.
Thanks again, Everyone.