I tried to upgrade the 64gb ssd on my ep121 and bought a crucial msata 256gb ssd. I installed it with no problems and was able to do a clean install of windows 8 pro 64 bit on the drive. But then, I discovered that my win 8 was an upgrade and would not activate on a clean install, so I had to do a clean install of win 7 home premium 64 bit (which is what had been running on my old system drive with no problems) and then do an upgrade install of windows 8 pro over that to get to use my windows 8 software. I had some driver problems when I installed window 7 and installed those before installing windows 8. Anyway, I finally got windows 8 up and running fine on my new 256gb ssd. But after a short while, windows 8 said that it had encountered a problem and was going to fix it and restart. It restarted, but soon it happened again. When I restarted the tablet, it kept going into the bios when I tried to navigate the bios to check the hard drive, there was nothing and it froze completely. I had to turn it off via the button only. It kept doing that many times. Never going out of the bios, no matter what. I put my old ssd back in and everything was fine. I put the new ssd in and the same thing kept happening. I had another new, blank crucial 256gb msata and put that in, and this time a bootup message showed when I turned on the computer that said- insert correct boot media and hit any key (I use a usb keyboard with the ep 121). It did that repeatedly and nothing helped. I tried connecting a dvd drive with the windows 8 install disk in it before bootup but it made no difference. I could not enter the bios or get it to boot from the dvd like it could before. Then, when I put the other crucial 256 gb ssd that already had win 8 on it back in, I started getting the same insert boot media and hit any key message. It won't go into the bios anymore or boot from the dvd. When I put my old 64gb ssd back in, it all works perfectly. What the heck is going on? I have bios 704 installed well before doing any of this. Is the crucial drive or size incompatible with the ep 121? But why did it work briefly? Any suggestions or advice would be greatly appreciated. Thanks.