Reinstalling Windows and Activation Keys

Hi Everyone,

I was fixing one of my friends computers and I had a quick question.
His laptop came with Windows 7 so I downloaded the official ISO from MSDN and activated it with the serial number on the little sticker on the bottom of the laptop.
Then, something happened in the next few days (not sure what. The computer was with my friend for the time) and I had to reinstall Windows again.

So my question is, does reinstalling Windows multiple times in a short period of time put him at risk for getting his serial key black listed?
I would like to point out that the serial is only ever installed on ONE machine at a time. Just his one laptop.

Thanks!