As with all electronic equipment, the router on your home network will eventually have to be replaced. As the router starts to fail, you may find that you're resetting it on a regular basis to keep it operational. You may also find that your data-transfer speeds from computer to computer are slowly dropping. These are just a few of the good indications that the router on your computer is looking for a route out of town, so to speak.
Document how often you reset your router to keep your network up and running. Resetting the router involves unplugging it and plugging it back in, or pressing the "Reset" button on the unit's rear. This should need to be done vary rarely, if ever, on a fully operational unit. If you find that you need to reset your router a few times a week, its time to buy a new unit.
Pay attention to the indicator lights on the front of your router. If your network is operational, the indicator lights should be a solid green color. If these lights are flashing, are red or are not on at all, you'll need to replace your router.
Verify that all of the computers on your home network are actually connected to one another. Try transferring files back and forth between machines, and make sure the computers are actually connected to your router's network. If computers keep randomly being dropped from your network, replace your router.