Q: Reinstalling Windows 8.1 under bootcamp

I've never tried it but I would expect it to be safe

and if it was not I would get sad because my win8.1 is an digital update of win8 which was a digital update of win7 that I org installed in bootcamp so haivng to reinstall win7 and then update would be a hassel

I have a feeling that it will not work, if you're reinstalling Win, you should use boot camp assistant to both delete and reinstall. Give it a shot, though, won't know unless someone tries.

should likely take a backup from inside windows of the data which is important as timemachine don't backup the windows partition