OK, here's what I've done so far...
1. I was able to remove Avast by using the installer. I am, however, now having problems with McAfee Security-as-a-Service which was previously installed and which I thought I had removed before installing Avast. I think McAfee is causing problems with the applications you're recommending I use being unable to communicate over the internet, as I will explain below.
2. I was able to download and restore the Start Menu shortcuts and the Administrative Tools Folder. I'm pretty sure those are working fine now.
3. I downloaded and tried to run (a) Uniblue Registry Booster and (b) the Microsoft FixIt but both programs refused to work. Registry Booster gave me a result that was like a '404'-type window in Internet Explorer. Wondering if this is directly related to IE's failure to launch? With MS FixIt, I got the error msg "Fix it troubleshooting cannot continue because an error occurred. We're sorry, but the program encountered an error trying to contact the server. Please try again later. [Code80072EFD]" The error msg was identical for both FixIt programs.
4. I launched IE and used the Network Diagnostic Tool, as the web page directed. The resulting 'Troubleshooting Report' error msg confirmed that McAfee Firewall is blocking connections, as I feared. Here's the message:
Diagnostics Information (Network Security)
Details about network security diagnosis:
Settings that might be blocking the connection:
Provider name: McAfee Inc.
Provider description: McAfee Firewall
Filter name: GUID_MFE_CONNECT_CALLOUT_V4
Provider context name: -
Network Diagnostics Log
File Name: 19AA3389-4422-4E3E-BBFF-CEB2BD191AE7.Diagnose.0.etl
Other Networking Configuration and Logs
File Name: NetworkConfiguration.cab
Computer Name: ZINJA-WARRIOR
Windows Version: 6.1
Time: Friday, August 19, 2011 5:56:26 PM
(The Geeks2Go site won't allow me to upload the 'diagnose.0.etl' file. However I am able to upload the 2 networkconfiguration logs, in case you think they may be of help.)
5. I attempted to go through WIndows Firewall to disable McAfee but the system wouldn't permit it. Here's the error msg:
"Windows Firewall can't change some of your settings. Error code 0x80070422"
That's as far as I've gotten, and I will continue working on it tonight.
I wonder, since RegistryBooster didn't work, would it make sense to try "Advanced System Care v.4"? I have used this program before. I ran a Deep Registry Fix just now and it showed 5549 'problems.' I have NOT taken any action to remove or fix these registry errors. It did generate a log file so if you think that would be helpful, please let me know and I will post it.
Thanks again for your ongoing help!