Missing XP style Start menu option in the Taskbar properties

When you open the Task bar properties and switch to Start menu tab, the "Start menu" check box may not be available and you're forced to use the Classic Start menu. This is due to a policy setting, especially if your system is in a domain. Contact the network admin to relax this setting. For a standalone, try the following steps.

Using the Registry Editor


Using the Group Policy Editor - Windows XP Professional

Related:  Policy Settings for the Start Menu in Windows XP