this solution below worked for me (or see my
blog post) :
get Windows 10 preview ISO,I used
Windows10_InsiderPreview_x64_EN-US_10074.iso
mount Windows 10 ISO under Windows 8.1 (double click or right click/mount),
copy .\sources folder from ISO to local HDD, say
c:\temp\
copy flash.ffu from the Windows 10 IOT ZIP to
c:\temp\sources\
folder then open a command window using Admin permissions (hit Windows-X, then A)
find the disk # of your SD card using diskpart (you have used # 2 above)
type:
dism.exe /Apply-Image /ImageFile:flash.ffu /ApplyDrive:\\.\PhysicalDrive2 /SkipPlatformCheck
BTW my first time at this failed however my 2nd attempt worked. Unsure if any bearing on it, but first time I'd formatted SD card using FAT32, second time using NTFS. Although I'll still be doing a dual boot VHD install to test Windows 10 when I have some free time, this worked for me and saved me a good bit of time.