I have 2 Precision M6400's running Windows 7 Pro and both are working fine on Win 7. I notice Dell does NOT support the Windows 10 upgrade to the M6400. I am not in a rush to switch right away, but I wonder if anyone here has been able to go to Windows 10 on their M6400? Searching the internet I've only found a little info that a few had no problem and a few had problems, short on details---but no solid info. Anyone here try it?