Method 1: Check Group Policy Settings
1) Run gpedit.msc from Run... prompt
2) Navigate the tree to User Configuration --> Administrative Templates --> System --> Ctrl + Alt + Del Options.
3) There should be four settings:
|Remove Task Manager||Remove Lock Computer||Remove Change Password||Remove Logoff|
Make sure each of these is set to "Not Configured"
Method 2: Editing the Registry
Note: This is necessary if you are running Windows XP Home instead of Windows XP Pro
1) Run regedit from Run... prompt
2) Navigate the tree to
3) If you see an item named DisableTaskMgr, delete it. This should restore your access to the locked items.