AutoIt/AutoItX is free and can be found here:
http://www.hiddensoft.com/AutoIt/
To disable mouse and keyboard input:
Set oAutoIt = CreateObject("AutoItX.Control")
oAutoIt.BlockInput "on"
Input will be automatically enabled when the script closes if you don't issue
an off command.
This function will have different effects depending on the operating system
used:.
Windows 95 No effect.
Windows 98 User input is blocked but AutoIt is also unable to simulate input.
Windows NT 4 (Without ServicePack 6) No effect.
Windows NT 4 (With ServicePack 6) User input is blocked and AutoIt can simulate
input.
Windows 2000/XP User input is blocked and AutoIt can simulate input.