If anyone has done this on an Optiplex 780 where the OS was installed under Legacy and they successfully switched to AHCI, please let me know what you used to accomplish this. I tried downloading the Intel PreOS install drivers for the it but as soon as I try updating the 2 drivers in question, it gets about halfway thru transferring the files and BSOD. I am running WINXP SP3. I also tried uninstalling those components and rebooting hoping it would ask for new drivers and that didnt work either.