My laptop no longer connects wirelessly! Please help?

Hello, a while ago, my laptop (Acer Aspireone, running on Windows 7, Google Chrome) could connect to my router effortlessly, allowing me to you use my laptop all around the house, including upstairs (the router is downstairs). However, recently, upon trying to connect, I was given the message “Unable to connect to the internet”. I went on to try to connect using my desktop (Windows XP, Internet Explorer), and that also failed to connect. I’ve had to revert to using an ethernet cable now, however that completely and utterly defeats the purpose of me acquiring a laptop in the first place! Please help me out on this one guys, it’s urgent! Many thanks, Alex.