So I finally got around to installing Windows (I haven't had Windows installed in about a year). Since I already had a working Debian install, I just installed Windows on an empty partition. I usually do it the other way around, but of course I wasn't going to reinstall Debian to use my usual approach. After the windows install, I found myself without grub in the MBR. This was totally expected, and one of the reasons I usually install Windows first. Recovering the MBR was far simpler than expected. I just popped in the Debian Etch installer, right after boot got to a terminal (Alt+F2), and did the following

mkdir /mnt/temp
mount /dev/sda1 /mnt/temp
mount --bind /dev /mnt/temp/dev
mount --bind /proc /mnt/temp/proc
mount --bind /sys /mnt/temp/sys
chroot /mnt/temp
grub

When grub loads, I then did the following:

root (hd0,0)
install /boot/grub/stage1 (hd0) /boot/grub/stage2

Then rebooted, and got a grub console instead of my usual grub screen. No problem: just do

configfile (hd0,0)/boot/grub/menu.lst

and the usual interface is up.
After my desktop loaded, I found the grub-install command that would do a better install than me:

grub-install /dev/sda

And then I had a completely normal boot screen. I just had to add the new Windows entry to menu.lst and I was set.
So there goes the ancient fear that installwing Windows after Linux is a pain. There are, of course, cases in which it is a pain (I remember once windows messed with my partition table and linux wouldn't boot), but this time I had absolutely no problems.

--
Felipe Sateler