powershell Startup script is not running on client machine

Hi,

We have a OU which has some computer accounts. We have a powershell script which sets the value of HKLM\system\currentcontrolset\services\usbstor  - start - 4. I created a GPO in which this script is set in startup mode. I have applied this GPO object to the OU. In parameter tab i have kept it blank. But this scrpit doesn't run all on any of the machines. I have checked the script running manually and it works.

I have gone through the microsoft blog's and have performed in that way also but no output.

1. What more setting i need to do on GPO object ? 

2. Or where should keep the script in server sysvol folder ?

Thanks