If you do not have USBstor in service in registry then surely...USB devices is not installed on ur system...
Do the following to remove restrictions(i.e. to enable) on USB usage...
If a USB storage device is not already installed on the computer, assign the user or the group Deny permissions to the following files:• %SystemRoot%\Inf\Usbstor.pnf
• %SystemRoot%\Inf\Usbstor.inf
To assign a user or group allow permissions to the Usbstor.pnf and Usbstor.inf files, follow these steps:
1. Start Windows Explorer, and then locate the %SystemRoot%\Inf folder.
2. Right-click the Usbstor.pnf file, and then click Properties.
3. Click the Security tab.
4. In the Group or user names list, click the user or group that you want to set allow permissions for.
5. In the Permissions for UserName or GroupName list, click to select the allow check box next to Full Control, and then click OK.
Note In addition, add the System account to the allow list.
6. Right-click the Usbstor.inf file, and then click Properties.
7. Click the Security tab.
8. In the Group or user names list, click the user or group that you want to set allow permissions for.
9. In the Permissions for UserName or GroupName list, click to select the allow check box next to Full Control, and then click OK.
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source:: *support.microsoft.com/kb/823732
Then u need to install the device and use it
