Mandrake 7.2 is ancient; it reached end of life in 2000
. It is, in fact, older than XP and completely unsupported.
I would suggest you get something newer, perhaps Mageia 4
, which is a descendant of Mandrake. When you spin up the install, it should offer you an opportunity to replace the existing Linux install. It may also solve this problem for you; when I installed Mageia on my Win7 box, it set up the dual-boot flawlessly.