You need to reinstall Backup for Workgroups because you have replaced your local hard drive or you are switching your account to a new computer. Once you have reinstalled the Backup Server, you can recreate the Backup Client account that was used to backup the computer running the Backup Server software. Use the drop down list to select the name of the Backup Client account for this computer.
If this computer was not included in the backup process, you need to select the second radio button and press Next.