To install the 2001 updates, from the CD simply select the 2001 option; if running from the web or E-mail, run ADV2001.EXE (requires a password - if you do not have it call us 888-923-3786 or send an E-mail to support@addsuminc.com).
This installation will automatically run an install program that will launch the Advanced Accounting engine. When you see your license, simply press the ENTER key and allow the process to complete.
The 2001 updates include the 2001 payroll updates. Once you installed this update, you are done. (Unless you have the Addsum Utilities or Quotes/Contacts in which case those each also require an update.)