If your laptop came with some other OS (XP, 7, or Vista) and you purchased a Windows 8 DVD/license
(full version) to install over that, then you may be able to reinstall Windows 8 using that laptop's hard drive in your new system.
If your laptop came with some other OS (XP, 7, or Vista) and you purchased a Windows 8 DVD/license
(Upgrade) to install on top of that, then you will need to purchase a new Windows license for your laptop's hard drive in your new system.
If your new case does not have a 2.5" drive bay, you should probably use a 3.5" to 2.5" drive bay adapter for installing the laptop drive into your new system. Something like
this
-Wolf sends