Getting the bootloader to display so I can boot different OS

[Dave Martini 1]

I  have a dual boot RHEL and XP machine. When I have the RHEL OS booted 
and I do a
shutdown -r now it reboots but it doesnt' show the grub splash screen so 
that I can choose
to boot from XP. When the machine is actually powered off and I power it 
on I get the splash screen.

How do I get the boot loader screen to  show up when I'm logged into Red 
Hat and want to switch
to XP?

Thanks very much.
David Martini
LLNL