The main problem with getting the best performance from your SSD is your mother board, specifically due to the ICH7 chip. If your board had the ICH7R version of this chip, you'd be be much better off.
The ICH7 does not support AHCI mode. Enhanced mode is not AHCI, sorry to say. A BIOS update cannot change or fix that. You can confirm this by reading the Overview section (1.1) of this document:
Since you cannot enable AHCI mode, or RAID mode, you cannot use the Intel IRST drivers. Also since you cannot enable AHCI mode, the Windows AHCI driver (msahci) will not load.
While you will lose some AHCI features, your SSD will still perform well in IDE mode. You won't have TRIM support without an AHCI driver, so you should test if you can use the Intel SSD Toolbox on your PC. I cannot predict if it will work or not, but it's well worth installing and testing, and if it doesn't work you can uninstall it. If the Toolbox SSD Optimizer will work on your PC, you'll have manual TRIM support, which will keep your SSD in optimal condition. Without TRIM it's performance can degrade over time.
just to add to mistermokkori's post.
It (TRIM) does indeed work with the standard IDE driver from Microsoft in win7. I experienced this first hand after testing an X25-V drive about 2 months ago. I used a similar motherboard without AHCI (ICH7 southbridge) and despite thrashing it pretty harshly, the SSD maintained read/write speeds very well.