Whoa! Wait a minute here! While this is technically possible, it most likely is illegal! A new motherboard, new RAM and new CPU equals a new computer! And according the EULAs (end-user license agreements) for almost ALL software, including operating systems, using the software on a new computer requires a new license! That is, you must buy a new copy of Windows to use it legally on this new computer. Not doing so is stealing and that would make you a thief, subject to a substantial fines and possible jail time for each EULA violation!
The ONLY exception is if you are using a full "retail", boxed copy of Windows you purchased separately at a retail store, or directly from Microsoft.
If that copy of Windows currently on that C drive (1) came with the old computer, (2) is an OEM version you purchased for that computer, or (3) is an Upgrade version you purchased for that computer, then using it in ANY other computer is illegal! Period! Don't do it! Buy a new license of Windows for this new computer, or use one of the many available free versions of Linux.
As noted, this is an industry wide policy for all software, not just Windows or Microsoft products. If you have other purchased software installed on that C drive, you may need to buy new licenses for your new computer. It is immaterial that you are using the same case, power supply, drives, monitor, etc. And technically, the CPU and RAM don't matter either. The new motherboard is the determining factor.