install windows first, or you'll get your bootloader screwed up...after windows, install mandrake. and oh, I think you shouldn't install the bootloader to main boot record (MBR), because according to what I've seen, it can cause serious problems. I'd suggest you make a small partition for the bootloader and install it there - make it primary partition after installing windows and then install bootloader (in Mandrake's install setup) to the active partition. that's all of the important things, I guess..
oh, and remember to make a bootdisk for your os'es...might come handy if you happen to screw something up big time
saves a lot of time.
1) install windows
2) make small boot partition, activate it
3) install mandrake, put bootloader to the small partition that's active
4) make bootdisks
if you ever happen to need to reinstall windows, then do this to prevent damage: make your boot partition unactive (not-bootable), activate windows partition (make bootable). then reinstall windows, and it won't destroy your linux/boot partitions...when ready, deactivate win-partition (make not bootable) and activate the linux's bootloader-partition again (make bootable). this might sound like a little hassle-thing, but believe me, it saves you more than much (I know, I've done it and thanked it since the first time). if you do the normal installation and not this, reinstalling windows crashes your bootloader and might do something else too
and this trick also keeps your windows's own bootloader untouched, which means that if you ever remove linux, you don't have to reinstall windows's bootloader, but only make the win-partition active (bootable) and it runs like in the old (bad