No, it's not time to call the vet, but if your computer is running like an overweight basset hound, it may be time to put a leash on some unwanted programs. These unwanted programs are classified depending on how they attach themselves to your computer.
Viruses are programs that attach themselves to other programs. They also replicate themselves and attempt to infect other systems.
Trojan Horses are programs that are embedded inside another program that appears to be something of value.