I work as the IT guy at a small private school.

I'm trying to help students buy inexpensive computers using a free OS 
and software.
I needed to test the latest free Linux on my workstation as a dual boot.

I installed Cheap-Bytes Fedora Core 4 on an WinXP machine's second EIDE 
drive.
The installation went fine but on reboot no GRUB loader menu showed, 
just plain old XP.

I tried this on an identical machine and got the same results.

I blew XP away on the second machine and successfully installed Core 4 
as a single boot.

I had previously successfully installed Cheap-Bytes Linux 10 for dual 
boot on a third machine identical to the machines that failed. I had the 
choice of the LILO boot loader in that case.  Core 4 only offers GRUB.

Is this really a loader issue or something else?

Any Ideas??  Can I resurrect the first machine with a boot floppy?  How 
would I configure?  I can't see the actual file structure of the machine 
that won't boot properly. 

One more question.  Where can I get a comprehensible and comprehensive 
tutorial on GRUB?