You should verify your Windoze boot disk before doing anything else. Make sure your floppy is before the hard drive in the boot sequence (see your BIOS screens to configure this). Put your boot floppy in the drive, reboot the system, and see if you can access your C: drive (note that you will not be running Windoze; you will be at a command prompt). You should also verify that your boot floppy has a copy of fdisk on it, since you will need that in order to re-write the MBR (I'm assuming Mandrake didn't make a copy of the MBR if it installed LILO there).
If you can access your Windoze installation and you have a copy of fdisk on your boot floppy, you can go ahead and delete the Linux partition. After deletion, insert your Windoze boot floppy. Reboot, and run fdisk /MBR to re-write your MBR (and remove LILO). If LILO has been installed in the root filesystem of your Linux partition, that's OK -- you don't have to worry, because LILO was deleted when you deleted your Linux partition.
Hope this helps.