I need to know how to reset user id and password on some computers I bought on an auction.

Reformat the systems. You'll either need to have a valid Windows CD or use a free Linux distribution.

The program available here (http://pogostick.net/~pnh/ntpasswd/) will let you delete the password. This program runs from the command line but is well documented and fast, just download, burn to CD boot and read and follow the instructions. With second hand computers reinstalling an OS and apps is always preferred. This way you know what you have and you can insure that all your software is leagal, clean and up to date.
If you are going to reinstall take a look at Linux Mint (http://www.linuxmint.com/), less of a tweaking job than Ubuntu or even Windows for that matter.

Which area of the computer is the password located? In the software portion or hardware portion?