Now I may look like an idiot in a Star Wars suit but as well as doing film extra work I also gained a Ph.D. in electronics. Let me therfore give you some pointers in how to make your WiFi signal travel further. Some may involve paying out for a bit of extra kit but many will cost you nothing at all.
The best way to actaually see what you are dealing with is to download a free programme called NetStumbler for the internet. This will actually show you what your computer can see and what interference is there to get in the way of your efforts. Showing for example what channels your neighbours routers are tuned to. You must NOT share your channel with anybody close to you, also try to keep at least 3 channels away from other routers
There are two major uses for WiFi, the first is to be able to use your laptop anywhere in the house or garden and the second is to set up a point to point arrangement so that you can make your network work in a shed at the end of the garden or perhaps to share your broadband connection with another house. Incidentally you need to be a bit careful if sharing your broadband connection as in some circumstances it is against the law! In the UK there are cable rules which say that one connection is for one household, this means that a signal may not legally escape from your home! Strange but true, so don't go telling the whole pub that your mate in the next village is able to share your network, apart from anything else they will hold you responsible for every loss of signal and every virus for miles around! Just do it quietly and keep the information to yourself!
The first way to get your signal to travel further is to check that you are not using the same channel as your neighbour. In the UK we have 13 channels to chose from (although many routers will choose the channel for itself without asking you). Try looking at the advanced options in your router set up screen and then set your channel to the other end of the band to any others that you see at and then try again. Your computer (as long as it is set up right) will find the new channel immediatly. I say as long as it is set up right as if you install Windows as its default USA settings you will lose the ability to tune to channels 12 and 13. You see only we in England are officially allowed to use channels 12 and 13 so if your system thinks that you are in America it will block the two extra channels from working. If your neighbour is using say channel 1 (if they use BTBroadband then that is what they will automaticall be set to) then you need to be at least 3 or 4 channels away, say channels 5 or 6 to avoid mutual interference.
If you want to get the WiFi to link to another house or the shed at the end of a long garden then try this, put both the router and receiver aerials on their sides - not pointing at the receiving site but at 90 degrees (sideways on) to the receiver. This makes your signal horixzontally polarised and reduces your received interference by a half! Horizontally polarised transmissions also travel further too as they tend to hug the ground better! We learnt that on the pirate radio forts in the '60's!
The next step might be to buy one of the 1W boosters that they have on eBay. Now this is a really good way to get extra range but remember that if you put the aerial at the end of an extension lead you will loose all the benefit as cheap extension leads can loose you 2.5dB per metre. Use a cheap 10 metre extension lead and you loose yes, 25db! That's about a fourtieth of the signal coming out of the end! That means that even using a 1Watt booster you will still end up with less than you started with! Boosters should be placed near to the aerial to work well.
More as soon as I have the time, if in the mean time you need help please get in touch and I will se what I can do to help. U.K.only I'm afraid as overseas rules are different.