Track your RAM usage. It can make a huge difference

To open the Task Manager press and hold Ctrl + SHIFT + Esc buttons at the same time up the left side of your keyboard and release.

In the following window that opens choose the performance tab as indicated by the red arrow in the screenshot below.

In this tab compare the Total value under the Physical Memory section against the Total value in the Commit Charge section.

In the example above the Physical Memory Total is larger than the Commit Charge Total and everything is fine.

If the Commit Charge Total was higher than the Physical Memory Total you would start to have noticeable performance problems.

NOTE: RAM is not the only factor that can cause a machine to run slow but is certainly one of the first ports of call if you machine is running badly.