Not enough physical memory on the computer.Fragmented hard drive, or filled up C drive.You should choose an appropriate antivirus for your protection. Using a 3 rd party bulky antivirus can also result in a RAM deficit.The presence of viruses or malware in the system can take up huge memory.Each app or software requires some amount of memory to run. There are various types of memory in a system, but we’re primarily focusing on RAM. For example, applications that are running in the background. There are many reasons why your OS is taking up most of the available memory, causing the system to slow down. Check on Amazon Common Causes of High RAM Usage