HDD config help please

Hi (Long post oops) Would like to start ordering parts for new build next week so need to finalize my confuguration.Also take into account as far as suggestionns go that I live in Deepest Darkest Africa and can't place orders on newegg and the likes ( Wish I could) ILL put links anyway so you get an idea. incase you can't see the image below the specs are as follows: 1- i7 920 ovc to 3.8/4GHz ( First time doing this) ----> http://www.prophecy.co.za/intel-i7nehalem-...ds-p-31955.html 2- Asus Rampage II Extreme ----> http://www.prophecy.co.za/asus-rampage-ext...i7-p-33692.html 3- EVGA e-GeForce GTX 285 -648MHz Clock, 1024MB 512-bit (Maybe a better ovc one) ----> http://www.prophecy.co.za/evga-egeforce-64...it-p-40953.html 4- Thermalright Ultra-120 eXtreme 1366 RT, retail pack with FDB fan ----> http://www.prophecy.co.za/thermalright-ult...th-p-33012.html 5- Antec CP-850 - 850 Watt Power Supply, nVidia SLi Certificated (Again maybe upgrade later to SLI) ----> http://www.prophecy.co.za/antec-cp850-watt...ed-p-34687.html 6- Antec 1200 case ----> http://www.ikonicit.co.za/index.php?target...;product_id=136 7- HDD - leaning towards Western Digital CAViAR Black 320GB 32MB cache 7200RPM type HDD's 8- LCD monitor 23/24 inch 5ms good contrast & resolution about 19*10 19*12 something not exactly sure yet? OK so been reading Nick_N's setup guide (Thanks Nick, very helpful) and decided because of cost/budget not to go with the best sys ie Raid0 or 10 on dedicated Raid card with those VelociRaptor's. Q1- will the diagram below be good enough with good quality sata 2 drives (No drive bigger than 320GB) Q2- do all the drives need to be the same size? Q3- DX9 not DX10? even though some games would work DX9 for FSX is best for performance? Q4- would desperately like to dual boot with W7 but assume the RC version (Not downloaded yet) is only one flavour? so not possible yet until the other versions come out October which means I would have to buy a version of Vista 64 now to upgrade later (BIG PAIN) currently only have XP and really tired of it (Going 64bit pronto!), new PC new OS's!! Q5- if that's he case how about this, I spend most of my time in the work boot anyway so how about in the interim while I wait for other versions I simply unplug the boot I don't need (Work or play HDD's) and power up in the one I do, or would that be a very bad idea or even legal? I have no problem paying for the software it's just bad timing for me personally and a inconvenience to upgrade later which I Loath to do, easy to corrupt a perfectly working sys! and then having to do it all again. So what do you guys think advice on the HDD config would be great. Thanks Tony