What CD's did you use to install Mandrake? If you downloaded iso images from the internet to your hard drive did you verify the integrity of the iso images before you burnt them to a CD?
If you were to be missing a small amount of the image then it could throw off the whole iso, and just might be the cause of your problem.
To verify the integrity of a CD image you will need to get the MD5 sum associated with the images, try getting them from where you downloaded the iso's, its a 32 character string of numbers and letters. To check the images
under Windows: http://www.linuxiso.org/viewdoc.php/verifyiso.html
under Linux: http://www.usalug.org/phpBB2/viewtopic.php?t=1215
The MD5 sum you get from the download site of your iso's should match the one's you generate from the images exactly
If the MD5 sums are not exactly
the same then you need to download the images again.