I have M6500. I have had it for over a year. It has an Intel X25-M 128G Boot drive, a WDC 500 G Second Drive and a Hitachi 1 TB 3rd drive (Media Bay). DVD is now in external case. I have tried to replace the 2nd drive (500 GB) with a new Crucial M4 256 G SSD. The laptop will not boot. The laptop goes through POST and just hangs with a black screen and a blinking cursor in upper left hand. I have tried booting the machine with just the boot drive, OK. Added the second SSD and no go. Added the second SSD as the third drive in the Media Bay, OK. I have validated that the laptop is operating in ACHI mode and always has been since I put in the first SSD last year.
As long as I use the first SSD as boot, and the two magnetic drives or the 2nd SSD as the third drive in the mediabay, it works. But I want it to be my second internal drive. This way I can switch out my 3rd drive for the DVD when I want to.
I have not had any other troubles with the laptop.
I have not found any errors in the BIOS log.
I do not ever get to the windows loading screen with the 2nd SSD as the 2nd internal drive.