Hi ,

Sounds like the account you are using doesn't have full admin priveleges . Does the PC just have the one user account ?

You can change all admin priveleges in control panel .

Click start > Control Panel > User Accounts > Manage account

If only the one account is set try the following :

Firstly turn off the guest account if it's not in use . Set a new account with full admin priveleges and delete the current admin account . You can transfer all files and settings to the newly created account .

The specific error message can mean either the account in use doesn't have full admin priveleges or the file or device isn't actually present to be accessed ( very rarely the case unless you've deleted something by mistake ) .

Hope that helps .