1) yes
2) it will work with ATA drives IF and only IF you have n ata raid controller.
mine has, its called GigaRaid... check if your motherboard supports is 1st!
3) you wipe both drives blank and then it thinks both drives are one... so 2x 40gb = 1x 80gb disk appearing in My Computer
4) doesnt matter
5) depends if you really need that kinda HDD performance...

i'd say if youre gonna do it, do it wth SATA drives... i bought 2x 160gb sata drives for less than 100quid...