I bought an old laptop and a new router however signal is weak?

It sounds like you may have gotten an 802.11b router. The signal strength and bandwidth on this router may be the problem. You can check easily enough, take the model number and plug it into a search engine and see what the specifications are. If it is a b router, upgrading to an 802.11g router will probably fix your problem. You should be able to get a g router for around $50.