I had to reboot my computer yesterday & when I did I got this message.

"One of the files containing the systems Registry data had to be recovered by use of a log or alternate copy. The recovery was successful"

What happened?

Windows has a thing called the "Registry". This is essentially a ... hmm, how can I explain ... it's a storage that contains all registrations for all software, all kinds of settings for installed software, stores your Windows settings (like background picture/color, resolution, # of colors, where icons are, how Internet Explorer works, etc.). This is contained on your computer. Windows "loads" the registry data when you boot up. It "unloads" this data when you shut down or restart. Sometimes, if the registry is not unloaded properly on shutdown, it will wind up corrupted or unusable. But, never fear, Windows stores a backup copy for just such a case. Sometimes a sector on your hard drive might go bad and it's right where the registry is stored...in which case, again, it would pull from a backup assuming the backup isn't corrupted because of it also :D

There are types of software out there called "Registry cleaners". For the most part, they are worthless, and half the time they do more damage than good. You may have heard of these. All they do is process the information in the registry to make sure it all seems valid.

If you lost your Windows registry, your computer would not be able to boot Windows (Windows wouldn't know how to act or anything about your system, what drivers are required, etc. - all this data is stored there). It wouldn't know what driver files it needed to load for your CPU, your graphics card, your network card or any of the chips on the motherboard. So, it's a very, very vital chunk of information to store. It should only be hacked/changed with professional guidance or by a professional user.

Hope this helps.