I don't know if it still holds true but here's what I found in one of my old notebooks...
Maximum number of local user accounts = 4,294,967,296
This was tested by someone on a 32-bit system many years ago.
Maximum number of local user accounts that can be displayed in Welcome Screen = 100
I wrote this information in some notebook many years ago but I forgot to reference or record the tester. I think he tested it on Win2K and XP Professional. The credit goes to him folks.
Every user account created will receive a unique number or ID which increments each time someone or something performs a delete-create a user account with the same name or create a new user account operation.
Limitations also apply to the hardware where Windows is running.
2I'd love to see a screenshot of that! – BloodPhilia – 2011-01-24T22:59:37.413
1There you go. It looks silly. – None – 2011-01-24T23:09:08.310
1Wow, thanks for taking the time to do that! I would hate to be the person at the end of the list, so looks like I'll have to find a way to enable the traditional login screen. – Connor W – 2011-01-25T21:49:11.410
1I've modifed my answer to add how to change the login screen. – None – 2011-01-25T22:19:06.430
Be careful if you are using switch user feature as some applications will be locked to the first person who logged in and locked the screen. – Phillip R. – 2013-02-05T05:13:10.710
@PhillipR. Not sure what you mean by that. Can you please expand on your comment? – None – 2013-02-19T22:50:25.823
User 1 logs on and a program launches at logon from startup folder or whatnot. User 1 locks the computer. Switch user is available for user 2 so they do that and log on. Some programs can become locked to the first person who logged on but locked the machine. Rebooting fixes it or forcing a log off of user 1. – Phillip R. – 2013-02-22T02:50:01.793