Open Windows Task Manager, click on the performance tab and monitor the graphs while using your computer. If the memory usage is high or maxed at 100%, the computer will operate slowly. If you have 4 gigabytes of RAM, then it's recommend that you at least double it to 8 GB. If you have a traditional hard drive, you may want to consider replacing it with a SSD drive in order to achieve faster loading times and better multitasking. Also, if your hard drive is almost full, that will cause slowdowns as well.