Tried again today (6 months later) and it worked!
I have an Inspiron 580 desktop with Windows 7.   I recently had to replace the hard drive and so am reinstalling all of the relevant software, including the Dell Support Center.   The 'aulauncher.exe' file appears to download OK from the Dell website, but when it runs I initially get a Dell Support Center Installation dialogue box stating that its 'searching for updates' but then a Dell Support Center dialogue box which states 'The download failed to install. Err: -29'.   Can anyone help?   Thanks
Dell Support Center - Fails to Install (Err: -29)