If you have a newer motherboard (no mention), and it's set up in RAID, the single drive will default to ACHI.
As long as the SSD is not part of a RAID array, like the 2x500GB are, TRIM is supported.
I THINK TRIM will work in IDE mode, but don't try it. TRIM is part of Windows 7, not the drive controllers.
However, get the latest Intel Rapid Storage Technolgy drive v9.6 here.
It's a self intall program, updates the chipset drivers, and has a little program to check RAID setup, etc. But, this is only for X58 chipsets!
There is a list at the bottom of the link for different chipsets, all Intel.