If you use Windows Vista or Windows 7 and are having problems with your computer, there is a MS tool called the System File Checker that will find missing or corrupted system files and automatically repair them. It also creates a log so if it can't for some reason repair a file, you can find another copy of the file and replace it using commands in the command prompt window. All the details about this tool and how to use it including the commands you need to run it are found in the Windows Knowledge Base under kb/929833.
Perhaps this can fix some of the problems some of you have had with CNX2 if it is system file related. In any case it only takesd a few minutes to run if no problems are found.
I had the kb file buried under some paper on my desk. I have used it from time to time and ran it just before I posted the link; it reported no problems also. I ran it because I ahd just installed and tried another utility called Fix It and wanted to make sure system files were still OK. I think the other important thing to do is to check frequently for updated drivers and software updates. I don't do this often enough, but did go out and check some Sw I use and sure enough there were multiple updates including new ATI drivers that seem to make my display run faster. The new ViewNX2 also seems faster to me.
SFC is also in XP, at least the Pro version - don't remember about Home. It's not clear to me what it does in XP. It may replace later versions of system files with earlier ones, even if the later ones are legitimate, which would mess up programs that need the later versions. I'd check carefully what SFC does in Vista/Win7 before letting it make changes.
The tool which is a Microsoft tool is just scanning for corrupt or Missing Microsoft Systems files. If it finds any corrupt files it fixes them and installs missing system files. It will not replace files with earlier versions, though if it found a file it could not fix and you attempted a manual fix you might. The link I gave you addresses Vista and Win 7 only.
I mentioned it because it is a simple tool to use and since it is a MS tool to fix its own system files, it is safe.