Cant change HDD configuration to AHCI?

Hi, I have a XPS 710 and I was wondering if I could change the HDD to AHCI over IDE...
I looked in the BIOS and there is no option to change to AHCI?
I was wondering if there is anyway to change to AHCI because it seems better and faster, I just wanted to get a bit of a speed upgrade. Also does it support SATA-II? Need to get another HDD because I am getting low on space.
It is a Dell XPS 710. Motherboard 0UY253, A00, BIOS version 1.4.1, date: 05/07/2007.
One 10K RPM
One 7200 RPM
WDC WD16 00AAJS-75PSA SCSI Disk Device
WDC WD16 00ADFS-75PLA SCSI Disk Device (I think this is the 10k but I am not sure)

Thanks!