Mandrake installs are flakey...
I used to use Madrake back in the day, but after around version 7 or 8, whicher they called "troptical" or something to that affect, I gave up on Mandrake, and went to Redhat.... I've heard of tons of people having issues installing mandrake, and if I remember correctly it's all about your hardware, or more specifically your chipset....
Do a google search on mandrake linux problems with installation chipsets etc... you'll see what I mean.
Switch to another Distro, I personally used to love Mandrake, but ever since they started releasing distro's with glitchy installers I was forced to switch.... I've used Redhat ever since, and I am amazed at how easy a clean install is, or a kernel update, plus RPMS are really handy when you don't have a complier on hand.
Just my 2 cents.