If I understand right, you have installed Mandrake 10.0 Official. You boot and end at a command prompt, but you expected a graphical user interface or desktop.
Sounds good so far, just don't have auto login selected. Try this:
At command prompt, enter:
If the command prompt says "logon", type your regular user name, hit the enter key. It will now ask for your password. Type your regular user password, not root password here and hit enter. If it appears no stars appearing when you type password like you see in windows don't panic, that is normal at logon. Now, your command prompt should change to reflect the name of the user you just logged on as followed by a $ sign to signify you don't have administrator privilage at this point. You may now issue the command "startx" without the quotation marks. This command will start X which is your gui. Once the gui is done loading, in your menu, locate "mandrake control center" and start that program. Under the boot section, there should be a spot for a checkmark for "autologon". This is to logon to a specific users graphical desktop at boot bypassing password and all, just straight to gui.
If you follow this and you get errors, rather than gui, post back, someone will help sort that out, but I think that you are good to go.