There are two low-level ways to create a GRUB boot floppy; typical usage:

In Unix
# cd /boot/grub
# dd if=stage1 of=/dev/fd0 bs=512 count=1
# dd if=stage2 of=/dev/fd0 bs=512 seek=1
In Windows
C:\> copy /b1 stage1 + stage2 grub.raw
C:\> rawwrite.exe grub.raw A:

Both grub-install and the prompt within grub can also be used. See Installing GRUB to your hard drive to get the basic idea.

It should be noted that dd is available on most rescue distributions (eg: Tom's rootboot) and is a good way to restore your MBR if you don't have a boot floppy. If you're even more desperate, you can download an ext2fs reader for Windows and get your stage1 and stage2 files that way.

1: The /b parameter for copy causes it to do a binary append of the second file.