boot from the CD.
before installation, there will be an option to boot a rescue mode - a command prompt of a real linux system, loaded into RAM from the CD. Either there will be an option, or if you type linux rescue at the boot: prompt and hit return
put a floppy disk in your drive, and mount it with this command
mount /dev/fd0 /mnt/floppy
if you get an error, try mkdir /mnt/floppy - the directory might not be there
then
dd if=/dev/hda3 of=/mnt/floppy/bootsect.lin bs=512 count=1 ; umount /mnt/floppy
where hda3 was your / directory
then reboot (type exit should do that.)
go back into windows, edit c:\boot.ini to have the following at the end:
c:\bootsect.lin="Mandrake"
copy the bootsect.lin file from the floppy to c:\
reboot, and choose Mandrake from the menu
....all of this is, of course, if you installed grub or lilo (linux boot loaders) to /
if not, you will have to install the bootloader yourself.
/sbin/grub-install /dev/hda3
would do that, again where hda3 was your /
