IDE = Legacy IDE commands
AHCI = Advanced Host Controller Interface.
RAID = AHCI + RAID features enabled.
You can set it to RAID mode and just not use the RAID features and still get the benefits of AHCI...
the thing is, it not booting is really weird.
Now, just to clarify, do you mean "windows gives me blue screens on bootup" or "the bios fails to post"?
If the bios fails to post, then your mobo has a problem, get it replaced under warranty (well, try a bios upgrade first).
If its windows giving you blue screens... that is because windows has seperate drivers for legacy IDE and AHCI. If your mobo is set to RAID or AHCI mode it will install both legacy IDE drivers and AHCI drivers, if your mobo is set to legacy IDE it will only install legacy IDE and NOT the AHCI drivers.
This means blue screens on bootup when you try to run AHCI... the solution is to install the AHCI driver before switching to AHCI mode in bios. that is a bit of a pain, so the simpler (but longer to implement) solution is to switch to AHCI mode and then do a fresh install of windows 7.