Okay, you did this with the Sis Card, which is supported just fine in the distro you are using, Mandrake 8.1... If the graphical install worked, then X will work too. The startx load had already passed through card recognition before it blew up on bitmaps.
Honestly, I have no idea what the 'bit map' nightmare is all about.
You can try to either create an XF86Config with the built in utility that Mandy used in order to do that cutsie graphical wirlygig, or hand hack the /etc/X11/X86Config-4 file.
try ./usr/X11/bin/XFree86 -configure
Then follow what it tells you to do next. Nothing is getting perma changed, its creating a test config file.
If that doesn't work, or doesn't work entirely... find out everything you can about your monitor, video card, and mouse and just bash away at XF86Config.