My brother suggests: "install grub to a cdrom instead of hd, then when he wants to boot linux put the disk in and it will display grub menu"
Also gave me this
From the Grub manual:
Something else you could try, if you think this would be too slow, is to
hide grub/lilo and have it give you about, say, two seconds to press a
key to unhide the boot menu. The default would boot WinXP and your wife
might not notice a two second delay.
Hiding grub, as far as I know is as simple as uncommenting a line in the
grub configuration file, which is located in /boot/grub/menu.lst
Here's an example file, running under Ubuntu "Hoary Hedgehog" Preview.
Check the timeout on the third line.
# Generated by grubconf-0.5.1
default=0
timeout=2
title Ubuntu, kernel 2.6.10-4-386
#:2

- type: 0 => linux, 1 => windows, 2 => other
root (hd0,0)
kernel /boot/vmlinuz-2.6.10-4-386 root=/dev/hda1 ro
## quiet splash
initrd /boot/initrd.img-2.6.10-4-386
savedefault
boot
title Ubuntu, kernel 2.6.10-4-386 (recovery mode)
#:2

- type: 0 => linux, 1 => windows, 2 => other
root (hd0,0)
kernel /boot/vmlinuz-2.6.10-4-386 root=/dev/hda1 ro single
initrd /boot/initrd.img-2.6.10-4-386
savedefault
boot
title Ubuntu, kernel memtest86+
#:2

- type: 0 => linux, 1 => windows, 2 => other
root (hd0,0)
kernel /boot/memtest86+.bin
savedefault
boot
When your terminal is dumb or you request GRUB to hide the menu interface explicitly with the command hiddenmenu (see hiddenmenu), GRUB doesn't show the menu interface (see Menu interface) and automatically boots the default entry, unless interrupted by pressing <ESC>.
13.1.3 hiddenmenu
— Command: hiddenmenu
Don't display the menu. If the command is used, no menu will be displayed on the control terminal, and the default entry will be booted after the timeout expired. The user can still request the menu to be displayed by pressing <ESC> before the timeout expires. See also Hidden menu interface.
the command "hiddenmenu" needs to be at top of grub where the timeout line and default line islike this
default=0
timeout=2
hiddenmenu
Which is pretty much what Undies suggested.