The HD2 (ATM) can't boot Windows 7.
But if you mean WP7, then no.
No because the HD2 can only hold one OS on its NAND, either WP7 or Android.
However, you can dual boot both OS's under two conditions:
It must not be a mango version (e.g nodo) .. because Mango locks up the SD and you can't use it for android. (AFAIK)
2- Android must be on the SD (an SD version).
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OnePlus One: Carbon 4.4 with Franco kernel.