See the OS X Help for "Adding a new user account to your computer"

Creating multiple accounts on the same computer in Panther is really handy and quite easy. All it means is that the new account has its own home folder (and thus all its own preferences). I use separate accounts on my iBook to keep my usual prefs safe. For example, I like to use a separate account when trying out a beta version. If anything is odd, I don't have to worry about my usual prefs or files getting messed up. Too, if one of my kids needs my computer for something, I don't have to worry about them messing with my desktop pattern, email settings, dock location, etc.

You can have multiple accounts running at the same time, and use the Fast User Switching feature of Panther to switch from one to the other. Rather cool, really

Anyway--back to your situation: The magnetmix test is important: something is choking your bandwidth (I hope it's not your ISP messing with filesharing controls). Go here, and test/check out your ISP's internet connection speeds http://www.broadbandreports.com/stest

What do you get?