i dont think a dell cd will work, they use the OEM cd's to install, the kind that were easily cracked and used to install on countless illegal machines. i believe it was called the corporate editions, but it was really just OEM installation CD's
i'd think you'd just need to find a suitable replacement CD from someone you know.
as for CD keys i have a funny story, my school bought like 400 xp-licensed pc's and then never installed XP on them, the first time they were plugged in the harddrives were wiped, all the machines were running windows 2000 and had 2 unit XP keys written on them-- anyone could walk into our library and just pick up a valid XP key that would never actually be used