Install Shield Update Service Agent

I have had a Dell Dimension 4600 PC for 3 months.  My ISP is Earthlink.  Total Access 2004, loaded on my system by Dell.  When attempting to use the Earthlink Update Manager feature I get the error message: "The InstallShield Update Service Agent has failed to install properly.  In order for the InstallShield Agent to install properly you must be the administrator on your PC and use your browser default security settings.  I've talked to both Earthlink and Dell technical support without success.  I am the administrator of my PC and have not changed my default browser settings.  I have no problem installing Windows XP updates and the McAfee Security updates.  I have tried getting the Earthlink Updates with my McAfee software disabled and enabled.  No success either way.  I have deleted temporary files and temporary internet files. I also get one of two script error messages each time I'm on the system.  I must click on them 4 to 6 times before they stop appearing: Script error Line 219 Position 5 or Script error Line 54 Position 5.  The specific Earthlink update I'm interested in is the Spyware Blocker which scans for and removes adware and spyware.  I would appreciate any assistance someone can offer.   Thank you.