Can you boot Windows OK? I've found that when I buggar the partition table on my machine, Windows is the first thing to complain.
Mandrake's DiskDrake is not the best program to sort out broken partition tables: if it can't find one it'll tell you so, and then just go ahead as if the whole harddisk is blank. Whilst this does (normally) give you a nice new partition table, it does wipe all the information previously there.
If you can boot into Windows, and you can do a seriously good backup, why don't you let Mandrake sort out the partition table for you? Make the backup; make sure the backup works OK; boot the CD and when you get to the partitioning stage, do it manually. Create your Windows partitions (blue), create your Linux partitions (green + red) and install Linux. MAKE SURE YOU MAKE A BOOT FLOPPY, because when you install Windows, you'll need it!
Oh, BTW, if you've got a cd-burner, I would seriously suggest Norton Ghost...I know someone's gonna say that there are really good Linux equivalents, but they require that you already have Linux installed! NG can be run from a Windows boot floppy.