Mandrake 9.1 located on a partition and you will need to remove taht partition..you can use Partition Magic or any other tool. when you remove the partition its auto will add the space to your windows patition so dont worry. If the Mandrake loaded will still pop up you will have to restore the mbr with the command fdisk /mbr
this post will help you to restore you mbr to you're windows loader..hope that will help.