Nolanrock100 :
How many times can you use the activation code for windows 8.1?
That depends on the terms of the licence.
If you purchased a retail version of Windows 8.1 you may use that licence on a single PC at a time. If you wish to move it to another PC, or sell the licence, you must remove all installed copies of the operating system.
If you purchased a system builder version of Windows 8.1 you may use that licence on a single PC only. You may reinstall it on that same PC any number of times. The licence is tied to the motherboard firmware, so changing the motherboard or upgrading the motherboard firmware may be problematic.