Source: http://lifehacker.com/5542012/extend-your-wireless-network-with-an-old-router-and-powerline-adapters
Photo by Andy Butkaj.
While we definitely love hacking our routers with new firmware, it does have a few downsides, most notably the fact that it's a pain to install. Furthermore, you may not be comfortable installing third-party firmware that hacks your device, if your router doesn't have the required firmware available. Technology blog Tested points out that a couple powerline adapters can help give you the same results by connecting your old router to your network through the power lines already installed in your home.
Essentially, instead of wirelessly "extending" your network, you'll be turning your old router into an access point and putting it in the dead zone of your house. It'll still need to be connected to the network, though, which is where the powerline adapters come in. Powerline adapters plug into your A/C outlets and connect to your network. You don't need any kind of electrical experience to get them working. You could, of course wire it up via Ethernet, but you probably don't want Ethernet cables running all through your house—so powerline adapters are a pretty awesome way to go.
You'll need to tweak quite a few settings on your router to make this work, and powerline extenders aren't super cheap—you could probably pick a few up for the same price of a regular wireless network extender—but if you have a house that isn't wireless extender-friendly (due to thick walls or a strangely shaped house), this is a great way to get wireless everywhere you need it. Hit the link for the full guide, and let us know your experience with powerline extenders in the comments.