I'm running Win8.1 on my M15x just fine with a little tweaking, and one big problem remaining. Other than that, it's running REALLY well. Most of the drivers I needed were picked up just fine during a clean install of the OS install. Dell's drivers on the site for the Alienware OSD stuff and some peripherals were fine, even though the video drivers and some other's were out of date. Nvidia's site fixed that fine. The real problem I have remaining is with the Broadcom Wireless 370 Bluetooth Mini-card, which the Dell driver's won't work with on Windows 8.1, and Broadcom's site won't detect the hardware correctly. Any advice would be welcomed.