I have been running Windows 7 for a long time and have never needed third party software. I make certain to reboot the system at least once a week and that alone seems to keep everything fresh.
Fractal Design R5 | Asus Z170 Pro | Intel i5 6600k | 16 GB G.Skill Ripjaws DDR4 2133 | Seasonic 650w PSU | eVGA GTX 550 TI | Samsung 960 M2 500 GB | Samsung 850 EVO 500 GB | ASUS Burner | Windows 7 64-bit