Boot off of extended partition?
 

I have an 80 gig hard drive, and 40 of it is being used for XP, and I plan on installing RH9 on the other 40. My quesiton is, can I make the available 40 gigs an extended partition and boot RH9 off of that?

Yes. Most emphatically, yes. However, I'm not sure that the xp bootloader will give you that option.
You may need to install grub, lilo, or some other bootloader (RH probably only gives you the option of grub or lilo). When you install the RH, be very careful to watch for the option to install the bootloader to the MBR (master boot record). Choose yes. A well behaved Linux distro (and I consider RH well behaved, compared to some others) will detect both win and Linux partitions, and correctly write the grub or lilo conf files so that, on re-boot, you will see a bootloader screen with the options to boot Linux or win. The default timeout (wait time for you to make a selection) is usually 10 seconds (in grub that's default 10; in lilo, if I remember correctly, that in 1/10 second, or default 100). To change the length of the timeout, edit /boot/grub/grub.conf in RH; (/boot/grub/menu.lst in other distros) to whatever value you want.

As a safety measure, if the RH installation offers you the chance to make a boot disk, TAKE IT. If ought goes ill, you'll need the boot disk or disk 1 of the install cd to boot into RH to fix things.

i had to install grub in order to boot my linux distros installed on extended partitions...i'm still not sure why i leave windows installed on my box, i never boot into it...