I'd agree with Jim that there's no need to fix things if everything is working, expecially in the Registry.
If, perchance, you'd like to look at the "official" answer to your "Come to that, what IS the registry?!" you might try Description of the Microsoft Windows Registry in the "Microsoft Knowledge Base." (This one covers all current systems, and has some info not really applicable to Win98SE.)
Anyone else with one of the newer op systems should take a look there, with particular attention to the difference between "regedit.exe" and "regedt32.exe." In Win2K and WinXP, there are registry functions that cannot be successfully changed in regedit.exe. You have to use regedt32.exe for some things. On the other hand, regedt32.exe does not have a "search" function, so you may have to use regedit.exe to find a "key" in order to go back to regedt32.exe to change it. (in the nutshell version of the difff.) Win98 and before don't have a regedt32 - I'm not sure about WinMe.
Everybody with Windows of any version should go to Search the Knowledge Base and "bookmark" it (add to Favorites).
Lastly, at Start - Control Panel - Add/Remove Software, click on the tab marked "Start Up Disk" and make yourself one (And don't forget to label and date it). Put it away somewhere safe. It will probably never be a help, but you'll feel better knowing you've done it - because you're supposed to. (And it doesn't hurt to make a new one anytime you make any significant changes.)