[quink]

I'd say Windows CE on ARM devices was attempt #1.

Lumia and Surface 1 and 2 were #2.

[WorldMaker]

1. Windows CE on ARM

2. Xbox 360

3. Windows Phone 7 (on leftover chunks of Windows CE) on ARM

4. Windows Phone 8/Windows RT

5. Windows 10 on ARM

So, by my count, this might be iteration 6? (Though maybe more like 5 Part 2.)

[mark-r]

I'm thinking specifically of the Windows desktop experience on ARM, so things like phones and Xbox don't count. But I didn't realize the Surface went through 2 iterations of ARM, so maybe this counts as #3? Or maybe it doesn't count at all since it was a watered-down version of Windows that couldn't run most apps.

[atesti]

Xbox 360 was PowerPC, not ARM