Your Computer Has a Mind of Its Own
Spyware, trojans and other pests contact other computers, and each pest is program of its own, therefore they use system resources such as CPU cycles, memory and an Internet connection.
Slow Computer
There are several reasons your computer may be running slow, but if you use it on a regular basis, then you're familiar with its noises, hang-ups and how it reacts. Older computers tend to run slower. Some applications cause computers to run slower. Computers are machines, they do not have moods. A sudden change in how your computer is running could be a sign of spyware or adware.