DLL C:WINDOWS\SYSTEM32\ADVPACK.dll Error

I downloaded an update to my McAfee virus protection program, and ran a clean-up utility that came with it.  After I ran the clean-up, my virus program stopped working.  After attempting to troubleshoot it at the McAfee website, I removed the whole program in order to re-install it.  My problem is that when I try to re-install it, it gets me to the download manager, and then I get the following error message:

 

The application or DLL C:\WINDOWS\System32\ADVPACK.dll is not a valid Windows image.  Please check this against your installation diskette.

 

The problem is first of all I don't have an installation diskette for the program I am trying to download, and now I can not run any setup file for anything.  I tried to install Norton from a disk, and I get the same error message.  I can not download any installation program from the internet.  I tried to run the diagnostic CD that came with my Dell, but that won't even run.

 

I also got the following error message when attempting something else:

 

Error Code 0x7e  WINDOWSXPSetup Setup library FXSOCM.dll could not be loaded or function FaxOcmSetupPrac

 

Now I don't even have an anti-virus program on my computer, and I'm afraid that I will end up with a real mess on my hands if I don't resolve this fast.  My daughter was on-line earlier today and a window popped up and said something about deleting files, then it completed deleted my favorites list in IE.

 

I have a Dell Dimension 8300 and I am running Windows XP Professional Version 2002 Service Pack 2.  Can anyone help me?  Thank you!