Windows .old Boot Up Need Help

> I installed windows RC2 Build 5744 A couple of weeks ago from a website,
> I did everything right, and even got my serial number for it.
>
> I wanted to boot into my old xp home edition, so I could remove windows
> vista and reinstall later.
>
> But, when I used the dual boot screen vista provides, I tried to boot into
> and earlier version of windows, but it says 'type administrator password'
> I tried all my passwords, I tried leaving it blank, I tried 123456....
> I do not know what the darn password is...
> I am frustrated now, can someone please help me?
> I never wanted it to have a password to prevent me from booting into my old
> version of windows... What is up with this?
> I am not going to purchase any software for this either.
>
> Also... a warning to people:
> Do not install Vista when you have a firewall enabled onto your xp version
> because if you do, make sure it is disabled or you will type 'netstat -b'
> into cmd.exe and you will see that the firewall's program stuff is still
> connected and will prevent some stuff from running because it's a firewall,
> and there's no way to stop it because it's a firewall that won't allow you to
> disable it like that. And if you goto your windows.old and try to find the
> uninstall for it, it will only bring up the one you have on vista which would
> be the CA Anti-virus like I have. unless you didn't install it for vista.
>
> Well anyways, someone please help me with the admin password...