Oooh, all five? I misread the post. ;_;

Fraps can't do that on one pc. You need a desktop recorder for that, and I don't know of a good one for that really. Either that or multiple computers.

If you can somehow work out how to record fraps on all windows. This is how it should be done.

At least two disks, one to play WoW off, using two directories max. Preferably one. And one to save fraps on, preferably scsi.
I think writing anything more then two per disk is gonna cause too much lag on a standard drive (Not to the game, but to the recorded movie.). So, this is probably one of the few things you can actually use scsi for. Which might work better. There's normally no reason to go scsi over s-ata for playing games, but this is something different I suppose. xD
And defi 4gb minimum, 6gb would be enough without much or any loss I reckon, above 6gb will probably not make much difference. Then I think hardware wise it should be able to pull the load while playing at decent settings. Videocard isn't important for frapsing, just for playing the game.

You still need to find a way to run fraps per wow instance first though.