Angry IP Scanner is a quick and easy way to scan for alive hosts on your network.You can get it at http://www.angryip.org/w/Download
Choose the appropriate version and just download and run it it doesn't require an install.
It will start up with your IP so let's say you're on a router and your ip is  192.168.1.10 just change the last digits and for example make it scan fromm 192.168.1.1 to 192.168.1.255 keep in mind it only goes up to 255. If you're not behind a router you can still scan your network for alive hosts.Just change the last digits again.