bairaghi, I would not go over whole computer lecture on you how the capacity of hard drive affect the performance of your machine. Please do little research (b4 you go ROFL over someone).
As unemployedguy mentioned, when you upgraded to wondows 10, you inherited most of the applications & clusters from old system. There might be threads/services running in the background which are no longer needed. A simple disk defragmentation, cleanup will help little bit to speed up your system.