Some time your windows PC go slow due to large garbage collection of the unused or temporary files such as windows history and unused windows error log files.
You can try the following free utilities:
CCleaner is the freeware tool that allows you to remove temporary files and folders from your system and make your PC run faster. It protects your privacy online and make your PC more secure. Additionally it contains a fully featured registry cleaner. Download link
It is also freeware utility which can be used to clean junk files and folders from your computer. You can remove history, cookies, cache, auto complete information for your internet browser, Windows temp folders and files etc. You can download from here.
With the help of Process hacker software you can find the hidden processes and enable you to terminate unnecessary processes. In additionally you have more control over running processes. Download from here
Above are the some free utilities help to make your PC faster, you can also see other free software on the internet.