Neither Lightroom installation nor Windows will move photos on its own. Something happened accidentally.
Did you by any chance import photos into Lightroom 5? Exactly what steps did you use to get Lightroom 5 up and running?
Yes, I did import photos into Lightroom 5. To get LR 5 running after installation, I selected Start > Adobe Photoshop Lightroom 5.2. Then, I noticed that many folders were created under the "C" drive and the folders were named by year and then under that, by date (in the format YYYY-MM-DD, probably the date of when I copied them from my camera to my hard drive). I never name my folders by date so that's why it came to my attention. That's why I think Windows (most likely) is playing tricks on me ... maybe during automatic updates, Windows has something set in the registry. Dunno.
Importing was your mistake. There is no need to import in this situation. But since you did import, you either chose to move the photos, or let Lightroom use its default import settings.
I would restore the backups of your photos to their original locations on the F drive and then have LR5 upgrade the LR3 catalog. Use File > Open Catalog in LR5
Oh, I misunderstood. I only imported 2 folders into LR 5 that were new .... I didn't import any of the folders that I had previously imported to my previous version of LR (LR 3). But, thank you for all your help!!!!!!