Tiger Woods 99 Golf Game?

I have tried other Tiger Woods Golf games, but always come back to "99". A couple of months ago, I had to do a complete restore of my system and stored some things on my external disk. I have been trying to get my Tiger Woods 99 back. The game CD installed and the game plays great. My problem, I have two disks of courses that I want to add on. I had them installed before the restore. Now, when I try to install them, I get messages like "games are not on disk" and Windows detects another installation on this computer and wants me to uninstall this before installing these. I can't find them on my computer so I plugged in my external hard drive and I found several dat and dll. files, but when I click on them, it tells me that these files are used by operation system and editing or modifying these files may damage my system. Now, first, why should these files, being on my external drive and the drive unplugged, have anything to do with installing these courses on my PC hard drive? If this is not the problem, then could someone help me get these courses installed? I surely would appreciate any help anyone can give me.
Red