Windows XP logon password is a must

If you are using LAlarm on Windows XP, you should enable Windows logo password if it not enabled. Otherwise a false (theft) alarm could occur. The windows logon password also protects your computer and data against unauthorized access.

See: How to enable Windows XP logon password

Win+L alternative

If your computer keyboard is old and does not have Windows logo key, you can not press Win+L to lock your computer. But there are some alternatives.

Using Task Manager:

1. Click Start
2. Select Run
3. Enter "Taskmgr" (without quotation marks)
   
4. Click Ok
5. Select Shutdown > Lockcomputer
   

Using a run feature:

1. Click Start
2. Select Run
3. Enter "rundll32 user32.dll,LockWorkStation" (without quotation marks)
4. Click Ok

Using a run shortcut:

You can create a shortcut instead, so that you just click on a shortcut whenever you want to lock the computer. The following instruction creates a shortcut icon on your desktop that has the equivalent function as pressing Win+L.

1. Right-click on the desktop
2. Select New > Shortcut.
3. Enter "rundll32 user32.dll,LockWorkStation" (without quotation marks)
4. Click Next.
5. Enter "LOCK" (without quotation marks)
6. Click Finish.

Furthermore you can assign a hotkey (combination) to the shortcut, for example, Alt-Ctrl-L. For detailed instruction, please see: How to Assign a Shortcut Key to a Start Menu Item