I'll start with the moral of the story first: Always keep your important computer files backed up, especially before making changes to your computer.
With a starting like that I am willing to bet that you have already figured out my problem. Computer failure. It all started because I bought a Olympus voice recorder to use for doing multi-media work (slideshows with sound) which are becoming so important for story-telling these days. When I plugged the sound recorder in to my laptop I kept getting errors that the device was not recognized, and that there were missing drivers. A lot of searching on the itnernet found that there are no drivers to be had. That lead me to think that the problem was with my version of Windows Media Player - I'm running Windows XP and the auto-update feature had upgraded my machine to Media Player 11.
So I tried to re-install MP11 thinking that maybe the device would get straightened out that way. No luck. So then I followed the Microsoft instructions to rollback to Media Player 10. It didn't work right and media player wouldn't work at all.
So now it is Halloween day and the ghouls are being very busy playing tricks with my computer. Being the genious that I am I then decided to simply re-install Windows XP onto my machine - a repair install that would revert the machine back to Media Player 10. In theory this is great. In practice the upgrades that the computer has done for a while now made the .NET Framework version up to 2.0, and the install disk re-installed version 1.0. The result was a computer that would not boot up into Windows. It would start, then hang up asking to go into "SAFE Mode" and no matter what I selected there the computer restarted and went back to the mode.
A lot of time with tech support from Dell, and then a subsequent driveto Albuquerque to have CompUSA create a data back-up of my photos, Email and other data had me finally to a point where I could safely reformat the hard-drive and reinstall Windows.
For the next five days I spent my spare time between assignments and sleeping working to re-install all of my programs; finding install software and downloaded files, finding registration codes to activate the software and so on.
Everything said and done my computer actually works better now than before the problems started. My copy of Adobe Acrobat 6 works once again... But if the hard drive had failed completely, rather than a system error, I could have lost a lot of things that I had not gotten around to backing up...