I followed the instructions at bleepingcomputer.com as suggested and am trying to run a clean boot using msconfig to disable non-microsoft services and all startup programs. msconfig reports an access denied error when trying to change a service.McAfee suite was previously installed on this system, but no longer functioned after "Additional Guard" appeared and was uninstalled because of a failed attempt at reinstallation. The McAfee software will not install successfully. AVG Free edition fails to install because it reports that Additional guard is already installled. I was able to run Malwarebytes Anti-malware to remove Additional Guard from the system and am unable to find any leftover files or registry keys. I scanned for rootkits but was unable to find anything. What else could be going on? Specifically:(1) What is causing the access denied error in msconfig (I get this despite running as an administrator in both normal and safe mode).(2) Where, if not in the registry, could the false information about Additional Guard being running be coming from?1 person got this answerI do too

Leave msconfig alone for right now. To make sure that all references to McAfee are removed, use its removal tool. McAfee Removal Tool - http://service.mcafee.com/FAQDocument.aspx?id=TS100507 Reboot after running the Tool. If the malware is truly gone from the system and you still can't install AVG after running the McAfee Removal Tool, you can try resetting the Windows repository that keeps track of security programs you have installed. Start>Run>cmd [OK] The command prompt opens. At the prompt, type: net stop winmgmt [enter] [Answer the Yes or No prompt with "Yes". See the message about the services stopping.] cd C:\Windows\System32\wbem [enter] ren repository repository.old [enter] Exit the command prompt and reboot the system. Try to install AVG again. If it fails, you'll need to post back at BleepingComputer to make sure your malware was really removed.MS-MVP - Elephant Boy Computers - Don't Panic!

Thanks for the help. Your suggestions did the trick.

Hurrah! ;-) I'm very glad to hear it. Thanks for taking the time to let me know.MS-MVP - Elephant Boy Computers - Don't Panic!

Awesome. Thank you. You saved me having to reinstall WinXP.