Either your Windows Installation diskette (floppy for Windows 95/98, use fdisk command) or your Linux installation CD will allow you to reformat your hard drive. I find the Linux disk editors easier and more versatile to use. Depends on your Linux distro, though.
Mandrake gives you a lot of file system options in the partition editor. To get there, start up on installation CD1 as if you wanted to install Mandrake. When prompted, select custom editing of partitions. You will then see a graphical display of your hard drive with all the partitions. To delete a partition, click on it, then select delete. Please note that no changes will be made until you click "next", at this time it will tell you it is writing the new info to disk.
There should be a simpler editing approach to just edit the hard drive partitions, but I'm a newbie myself and so I'm hoping that a member of this forum will come to my rescue, pretty pleeeeeze!?