rightho, typo there: it's definitely "startx".
Anyway, once you're in there's a screen in the mandrake control centre that lets you configure startup behaviour like whether to start straight into a user account and what GUI to use. I'm sorry I can't be more specific, but I haven't got a Mandrake distro installed at the moment.
(btw: for me part of the fun of linux is fiddeling around and stumbling on the sollution. If you can get into the GUI then you're safe anyway, cos now you know how to do it manually. Automating the process is nice but not essential, so have a look around. You can always ask again