In Knowledge Base article Q274435, Microsoft states:
"You cannot use the Logon Hours feature with Windows 2000 Professional or Windows NT 4.0 in a workgroup.
The Logon Hours feature is a feature of a domain user account. To use this feature, your computer must be a member of a Windows 2000 or Windows NT domain. You can specify logon hours on the domain user object on a computer that is running Windows 2000 and on a domain user account on a computer that is running Windows NT. You cannot specify logon hours on a Windows 2000-based workstation, a Windows NT-based workstation, or in a Windows NT Server-based workgroup environment."
This simply isn't true!
While the functionality is NOT available in the GUI, it is available in the NET USER command, as I pointed out for Windows NT, in tip 1026.
To restrict a Workgroup user to only logging on between 8AM-5PM, Monday through Friday, open a command prompt and type:
net user <UserName> /times:M,8AM-5PM;T,8AM-5PM;W,8AM-5PM;Th,8AM-5PM;F,8AM-5PM
For additional information on the net user command, see tip 2815.