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#11
The average computer user would not perceive any performance difference between Legacy IDE mode and AHCI mode.
However my personal opinion is that if you have a modern SATA hard disk why would you not want to run it at it's full potential? There is no good reason why your computer (nice rig by BTW) should not be able to run the disks in AHCI mode, and running in ancient IDE mode is just geek-wrong!
But here is what occurred to me: If you are going to run your computer in AHCI mode it is important to make that BIOS setting change BEFORE you install W7. If you did not that may explain the symptoms.
While clean installing W7 in AHCI mode is best, you can try and change over afterwards. See here: AHCI : Enable in Windows 7 / Vista