Once again thank you for putting me on the correct path to resolve this issue. This is my final posting regarding these errors and installation issues.
It finally dawned on me last night that there simply was something wrong with the administrator rights level account called "Ross Warren" on my computer, as AutoCAD 2011 would run just fine under the other accounts.
Perhaps some registry keys were messed up over the years, either my me or by using programs to clean the registry such as CCLEANER.
So, I backed up all my documents to an external drive (just for safety), then I logged on using the "real" Administrator account (which I had unhid so that it would show up as a choice during normal boot up - you can Google "Unhide the Administrator Account" if you want to know how to do that).
I used the real Adminisrator account to DELETE the "Ross Warren" user account. (It gave me options for saving the "Ross Warren" account's documents and desktop in a folder on the Administrator's desktop.) Then I created a new "Ross" account with administrator privileges, and then copied the data from the folder on the Administrator's desktop into the correct places in the "Ross" account.
Prior to this I had installed AutoCAD 2011 using the "real" Administrator account. It had installed fine for the most part, but I did get an error when it was installing the FARO LS driver. (It said An Error occured durign the installation of assembly 'policy.1.1.FARO, LS, version="1.1.406.58", type="win32-policy", processArchitecture=x86", publicToken="1d23f56ba800ab") I'll discuss that error later in this posting. But otherwise AutoCAD 2011 installed just fine AND I could run it using the "real" Administrator account. I switched the user to be the new "Ross" account and tried to run AutoCAD 2011 and it runs it fine as well.
So, my thinking here is that something somewhere was garbaged out with that "Ross Warren" account, even though I had never had issues using it before to install and run other programs.
I Googled for "FARO installation fail" and found a few discussions about it. I then got out of AutoCAD, logged on as the "real" Administrator account and navigated to where the FARO .msi file is in the Support folder and ran it - after I had deleted three references to the FARO driver as recommended on one of the pages I found in my Google search. I have no idea if runing the .msi file really cleared up anything with AutoCAD, but it did reinstall those three references to the FARO driver in the Windows/SXS folder.
I did some more digging and the FARO driver seems to be very specific for using certain 3-D scanners to input digital data into AutoCAD. Correct me if I'm wrong, but I assume as long as I don't attempt to use such a scanner it will not affect my running of AutoCAD 2011.
I'm not sure why the FARO install failed. I did not notice it failing before when I had attempted to install AutoCAD.
But anyway, I'm just happy at this point to be able to run AutoCAD 2011 under all three of the accounts on my PC, even including one I called, "Limited_User", which as the name implies, is a limited rights user. Aside: Note that to get it to run on the Limited_User account I had to copy all the files and subfolders in the C:\Documents & Settings\Administrator\Application Data\Autodesk\AutoCAD 2011 folder to the same folder for the Limited_User account.
So, at the end of the day, all my problems regarding the .NET Framework not getting the proper rights it needed to the registry seemed to stem from installing it from that one user account which had something messed up in it (even though it was an administrator level account).
In the future, when installing any other products, I will log on as the "real" Administrator account just to be safe, even though I now suspect that using the new "Ross" account would work equally well.
Thank you again for all your help. It was your suggestions about doing the custom install and unchecking the box for Migration, and then trying to run it with a different user account that put me on the right path.
For future readers of this post, I cannot stress strongly enough that to completely uninstall AutoCAD from your PC, in order to make it clean for a reinstallation attempt, you need to carefully follow the instructions on this page:
And also, you may want to completely UNINSTALL any virus software you have, as I found out the hard way that disabling real time scanning on Microsoft Security Essentials still allowed a process to run called MsMpEng.exe, and only completely uninstalling it took care of that issue. Finally, just for the heck of it, I did turn off my firewall during the installation. Of course as soon as you are done and AutoCAD is running, turn your firewall back on and reinstall your virus software in short order.