Unable to Create Bootable USB Disk - Need Help

I know I must be missing something easy. I really hope someone can help me. I have a LexarMedia 128MB USB JumpDrive. I managed previously, through lots of effort which I obviously can't duplicate, to create a bootable drive using mkbootdisk in Mandrake 9.2. Using this, I installed FC1.

I am trying to find and understand a generic way of:

1. Partitioning the USB key
2. Creating the filesystem.
3. Copying the diskboot.img files
4. Booting linux from the usb drive

So far I have tried the following:

sfdisk /dev/sda

   /dev/sda1 : ,,b,*
   /dev/sda2 :
   /dev/sda3 :
   /dev/sda4 :
   y
sfdisk -l /dev/sda

Device Boot Start End #cyls #blocks Id System
/dev/sda1 * 0+ 983 984- 125951+ b Win95 FAT32 /dev/sda2 0 - 0 0 0 Empty
/dev/sda2 0 - 0 0 0 Empty /dev/sda2 0 - 0 0 0 Empty

dd if=/dev/zero of=/dev/sda1 bs=512 count=1
mkfs.vfat /dev/sda1
mount /iso/FC2/FC2-i386-disk1.iso /mnt/cdrom/ -o loop
mount /mnt/cdrom/images/diskboot.img /mnt/floppy/ -o loop
(at this point usb drive is already mounted at /mnt/removable)
cp /mnt/floppy/* /mnt/removable

Pressed F12 on startup to get boot menu
Selected USB drive
Displayed message is "This disk is not bootable..."

I can open the usb drive in Windows or Linux and read the contents. It all looks OK, but obviously this isn't working.
Anyone know why?