but my mate has an oem version of windows 7 on his pc but his hard drive has failed and i was just wondering
if it can be wiped of the broke drive then installed onto a new drive with same product key?
Shouldn't be a problem.
Replacing a crashed hard drive would not constitute changing the OEM product substantially enough as to void the OEM license, and......
I don't suspect that you are the only person ever to have performed this task.