I might be wrong, but it reads like,, you have 2 HDD's and 1 SSD
You are trying to setup Raid 0 on the SSD?
You can't, you need 2 drives.
2nd, RAID or AHCI should be selected in the BIOS first, it's just easier.
This should also not create any issues with installing Windows 7 to a single drive.
You need to build the array first anyway, by hitting Ctrl-I (on intel board, others might be different).
I would certainly advise setting up a mirror, with External Drive Backup. Definitely not a bad thing to do.
I would not setup a Raid 0 however. Due to minimal performance increase (in everyday use) and no redundancy.
Greg's advice is not bad or wrong at all. Just another way of doing it.
I have 4 drives in my system...
I broke my Raid 0 because it was wasting space and there was not much performance increase, but have a Raid 1 for storage redundancy, and it has saved my ass once already.
PS. I would also agree not to setup Raid 0 on SSD either. I have not used SSD, but I assume the results might be the same, If I had the money though, I might try it just to see, but would probably disable it at some point.