MAC Mini hangs in booting on rescue media

Build 6525 for PC

I created a bootable USB from my HP laptop (Win 7) and mounted it in into my MAC mini. USB device is recognized as a bootable device, but when i try boot from it the mini freezes.

MAC mini is bootcamp to Win7.

I want to make a copy of the entire or disk or only the bootcamp partition.

Any ideas / feedback on how to get MAC mini to boot from USB rescue media is highly appreciated.

Kind regards

Anders