Need to do a Factory Restore but lost all passwords so blocked

I need to do a Factory Restore of my laptop. I can't get to the Repair Your
computer option because I can't even login. The username that comes up is
not the one I use. There are 3 choices of usernames, Guest, Administrator,
and the 'name'. I tried my password, which I was sure was right (but clearly
isn't) into all three accounts and it is wrong. I used the 'help' advice to
change one of the accounts passwords, and now I'm getting 'acount disabled'
when I try to get in to do the factory reboot. I can't get in!

I am the only person who uses my computer. I don't need more than one
account. Plse, can someone hlp me break into the thing so that I can do the
Factory Restore, and then just have a nice, simple, ONE account??
Thanks.
Vista Basic. Dell laptop.