Another way of improving the signal would be to add an external aerial, which screws into the existing socket. Beware, some routers do not have removable aerials, and there are two different types for those that do. Best to take your router along & try it in the shop.
Otherwise, there is a very cheap and simple method of improving network speed and reliability. Its a long piece of plastic, with metal inside, and plugs into both your router and the PC. You can even get them in all different colours. ;-)