Changing Administrator password with guest account

Hi I recently have come upon a dell precision 670. The thing is, is that the administrator account has a pw and I can only access the guest account which will not allow me to install anything. My dad had gotten this computer from his work and it's a fairly good one, but this also means that we have no cds or anything that came with the dell, even the xp sticker got taken off. So is there any way to change the password with out having to wipe the drive or buy outside software?

Here: http://www.techspot.com/vb/post633339-2.html
Using the bootable "Live" CD

Here's another one (Safe mode, Administrator access required though)
http://www.kellys-korner-xp.com/win_xp_passwords.htm