Help! Got a new-to-me laptop from my folks...went to do a quick wipe of the HD (keep windows, wipe data) and all was working fine. Then I hit 88% installed. Restart...back to 64% installed...climbs to 88%...restart...back to 64%...wash, rinse, and repeat. Don't have the windows activation key (it's somewhere in the software I think, but i don't know how to get out of this loop!).
What version of Windows? How are you trying to reinstall? Your best bet is to make an install USB from the Microsoft web site (search on Media Install Tool). You can do this on another computer. Make sure you are at Microsoft.com and search there. You should be installing Windows 10 as all other versions are not supported. I would select the option to competely wipe the disk. That will erase everything but it sounds like that is what you want to do. Ask if you need more details. I assuming the computer you got is not too many years old.