Windows 7, XPS 420, and SSD

I'm trying to install Windows 7 on an XPS 420 with an SSD.  The problem is that the system is not recognizing the SSD as an SSD.  If I set the BIOS to "Autodetect RAID/SATA", then when the installation is done, the disk is detected as an "ATA" device, and stuff like disk defragmentation is turned on, and so on.  If I set the BIOS to "RAID ON", when the system is installed, same thing happens, disk defragmentation is turned on, and the system doesn't seem to know that the disk is an SSD.  In fact, for "RAID ON", the disk manger wants to call it a "basic disk", whatever that is.

Is there anybody out there that can give me some advice on how to end up with a system that knows that it has an SSD, and so will send TRIM commands to it, and will turn off the stuff that decreases it's life?  I understand that some people can turn on AHCI in their BIOS, and this takes care of it, but I don't have that choice.

Is it something with installing with the BIOS "RAID ON", and then doing something after that?  Installing with BIOS "Autodetect RAID/SATA" doesn't seem to offer any help, since the SSD is just treated as an ATA disk, so the "RAID ON" path seems to offer more hope.

Or is there another BIOS setting that I'm not seeing?

This is frustrating, and even though the installations are pretty fast, it is worrying me that Windows 7 is not able to determine that it is installing onto an SSD.

Thanks for any help, someone out there must have gotten this done.

-Roger