Originally posted by SlipStream
So I take it that
Orcs have hte most power.
humans have what
Knight elves have what.
and the undead have what. ?
I don't have Warcraft 3 yet so I am a little behind. 
But it sounds like the Orcs do more damage as fare as hand to hand combat go. I think.
Everyone seems to like the Orcs best
Every race is balanced to have its own advantages and disadvantages. Orcs have more tough units, but they are expensive, and their air unit sucks (as well as their ability to combat air). Bloodlust is what gives orcs their kicks really.
Humans, as always, have adaptability. They can quickly speed build a structure by assinging more peasents to the task. The arch-mage spell Mass Teleport is one of the few reasons I play humans at all however.
Night Elves have three great units IMO. The huntress is a cheap unit that is availible almost right away. She can completely decimate the other races starting units. The chimeras have a devasting ground attack, but cannot fire at air, making them somewhat weak against an aerial assault. The dryad has abolish magic (or... dispel... something like that), which is great to have along as autocast.
Undead are like the zerg... they work better in swarms. Necros are my favorite, due to their ability to turn a battle once it gets going. After a few corpses, they can raise

of skeletons. In no time you'll have 50 or so skeletons bearing down on the enemy. Frost wyrvens are also great due to their ability to freeze, and temporarily shut down towers. They can also slow units.
As for the last night elf mission, just make sure you hold your allies town for as long as possible (send wisps to build moon wells (on autocast), protectors, and help with repairs). When the time arises that you must defend your own base, gather all your forces around the healing well, and build protectors... lots of protectors. keep sending furion to the merc camp on the right to buy mercs (trolls?). You should have all three gold mines entagled, giving you lots of gold. At the last 30 seconds, uproot all your buildings, and send all your wisps on repairs, to keep them at bay for the last critical part of the mission. Dont worry about archimond coming to your base. He arrives at the Circle of Power just as the mission ends.