my 2 cents...
-get norton ghost or some other drive imaging app
-buy another drive, 500 GB drives are cheap now... or a 1 TB
-copy all your data files from your existing troublesome drive to this new one... make sure to not copy any apps, you can copy over installers, just not the apps themselves.
-nuke your old drive, do a complete format (not just the quick format)
-install a clean copy of the OS on the reformatted old drive, do the all the fun OS updates
-install norton ghost, do one image then schedule it to back up every 15 days or every month ... let it create these images on folder on the new drive
Now you can fart around with all those nasty installs... just install any apps on the old drive... and only ever save data files to the new one.
If you ever get into trouble, you can back out all the way to a clean install (the first one you did... which has all the updates). It takes about 5 minutes or so to restore an OS image... as opposed to the 45 or so it will take you to clean install.
In general, its good practice to keep your data files away from the drive that is used to paginate memory anyways.
The very very very worse case is that the old drive dies a horrible death... but thats OK anyways, all your data is on the new one.
Should you ever want to archive/backup all your data... you can mirror the new drive to yet another drive or an external drive... and avoid all the issues of OS and applications altogether.