Many registry needs system reboot. With this tweak you can get around with that problem. You can reintialize your Windows XP registry using this tweak.
Press CTRL + ALT + DELETE, to bring up the Windows task list. Highlight 'Explorer' and click on 'End Task', if the Shutdown screen is shown, click 'Cancel'. After a few seconds an error message will popup, click on 'End Task' and the Windows explorer will be reloaded along with any new registry settings.
For Windows NT ,2000 or XP, press Ctrl + Alt + Delete and select "Task Manager". Choose the "Processes" tab and locate the "explorer.exe" process, highlight it and click "End Process". Select 'File -> New Task', then enter 'explorer' and click OK.