In windows Start > type msconfig and press enter to run msconfig It will show you what programs and services are started when booting your computer. Remove all programs that you are not aware of. Remove all from all unknown publishers
When you are using the computer
Press Ctlt+ Alt+ del and start task manager to see if any suspicious programs or services running.
Check if any program takes excessive memory
Press right mouse button on the application and end task.
Select and end process in process section.
Your computer can crash if you stop an important system procces.
This only removes programs from current memory.
They can run next time you boot up.