Hey all, I went and did a stupid thing (my first ever) I went to load the 4.9.3 upgrade, but I copied the files over my 5.0.1 install. Everything disappeard until I went back and copied the 5.0.1 upgrade over that. However, now I can't login into those sites. Any suggestions (besides being more careful in the future).

You've learned that you cannot "downgrade" a DotNetNuke installation. Hopefully, you've also learned that you should make backup copies of your website's directory AND your database before starting any major work on a site. You might consider that adding a new module is major work.

In you're case, it is likely that you have managed to write over the web.config file with one that contains an incorrect MachineKey. If you have a backup of your web.config, you can find the MachineKey there. Copy it into your current web.config. (Make a copy first!)

If you don't have a backup, register a new user with a known password. Then look in your database, copy the encrypted password and "Salt" from the new user to the corresponding fields for your host or admin user. That should allow them to login with the same password as the new user.

For other users, it may be easier to reset their passwords manually. Hopefully there aren't many. I suppose that you can set every other user's password identically. If you make it look like a random password, people might not realize it. Doing this depends on the actual security you need on the site.

Hey Joe, thanks I did a restore and checked the file, now the site thinks it's being upgraded. The message appears that the site is unavailable. Any suggestions?

Did you do a restore of both the database and the website directory?

Hey Joe, I was still getting the error even after I re-installed the database. So I re-initiated the 5.01 upgrade. This allowed me to get in with a secondary SuperUser account I created on all of my sites (just in case) and it worked. I than was able to reset all users and passwords.
Word of caution to everyone, this is a good reason for making backups and another SuperUser account...

Glad that you got it to work.