The files on that 500 gb storage drive should still be available for you to view, copy, move, delete, whatever when you connect that 500 gb drive to the new PC.
Do you have a Windows license for the old PC and another for the new PC??
Windows OEM licenses are tied to a given motherboard. Retail licenses are not, but a retail license can only be legally installed to 1 PC at a time--not 2 simultaneously.