You are not running it as administrator. The title bar of the Command Prompt is supposed to have the text 'Administrator: C:\Windows\SysWOW64\cmd.exe'.
Try right-clicking the install.cmd file and choosing Run as Administrator from Windows Explorer instead of PowerDesk. If it still doesn't work, then something more serious is borked. Enable the Administrator account in User Manager; login to it, disable UAC for that account, and run install.cmd there.
thanks very much. I had tried running from Windows Explorer, and running as 'the' Administrator account. What I had not done was disable the UAC. That did the trick, and the sidebar is installed. Thanks again.
"A man is not old until regrets take the place of dreams." -- John Barrymore