Windows 10 booting from external USB hard drive for testing compatibility...

[srandy]

Windows 10 booting from external USB hard drive for testing compatibility. I have Windows 10 installed on an external USB hard drive, just wanted to know if windows 10 would do anything to my internal hard drives once it was running. e.g. write/corrupt files on my Windows 7 main hard drive.

 

[Colif]

It shouldn't do anything to files on hdd as its not installed on them. Only chance that would have happened were if they attached when it was created, but it would just see them as storage drives and mostly ignore them. I have been wrong before but you should be fine.

 

[geofelt]

I doubt you would have a problem.
But... why not disconnect the internal hard drives, just in case.