There are ways to amplify Wi-Fi or at least expand it out a bit.
1: You can use a repeater. They are good to use as long as you put the repeater in a good spot where it can get full link speed to the router, and where the signal isn't lossy. However, repeaters do cut the available bandwidth in half, due to their nature. So, if a link is 54Mbps, the repeater will use half of that link for communication to the PC (or PCs, in which case the link goes slower) and half of the link for communication to the access point unless it has a second radio on it.
2: You can use High Gain Low Noise antennas. You can buy these around online that should work with almost every router that has a detachable antenna. The ones that come with routers are often times just cheapo antennas that add noise to the line and have short range. These antennas you buy are only needed at the Access Point UNLESS the access point and the PC are that far away. They can be bought for indoor or outdoor use, and can be directional or a spread.
3: You can get a better router. The ones that are better support MIMO and even SRX. These ones come with more antennas. I have a Linksys WRT54GX which is a super G router as well, and it is strong enough to where it blankets 1/4th of my neighborhood. In some odd times, I've picked up my network and have gotten brief connection to it 3 miles away (atmospheric disturbance?). So have my friends as well. Don't forget, the less advanced the router is and the less antennas it has, the shorter the range will be and the more dead spots you'll find, and in return, the slower the speed the farther you are away.
4: You can make an cantenna. Though not legal for use in the US (due to I think an FCC thing) they can if made properly and used properly (also a health hazard in a way) can send Wi-Fi quite a ways away, more like a mile or two. If you know how to mod satellite dishes, you can send Wi-Fi 20+ miles away.
I suggest either 2 or 3. I don't suggest trying #4 as while it does work, it is dangerous and possibly illegal based on where you live. #1 will work if you're not expecting to be having large files travel throughout the network or are keeping a 6Mbps or less internet connection, or if you're willing to shell up some money.