Execute QTP script. in locked machine

Start--->Run--> Type 'Regedit'
Change the following registry settings..
Goto following folder..
HKEY_LOCAL_MACHINE\SOFTWARE\Mercury Interactive\QuickTest
Professional\MicTest
Locate the key "SkipEnvironmentChecks"
By Default the value will be "0"
Change the value to "1" and restart the QTP.
Now QTP will run with system locked.