I am not certain just what your configuration is on your laptop or on your modem/router.
The thing is that depending on the particular hardware, this stuff can be quite directional.
Almost all laptop units with built in wifi are going to be a compromise in terms of how they managed to cram the stuff in. The ones that I have worked on have an antenna around the edges of the flip up LCD display unit and, from looking at them, I would deduce that they would be quite directional.
The PC card units frequently just have an antenna in the plastic end of them. So, I would expect them to also be quite subject to changes in effectiveness depending on position and orientation of the computer.
What I am saying by all this is that, if you have a utility that shows real time signal strength, you should experiment with positioning of computer and router and orientation of antennas if possible.
Also, keep in mind that if you are in different rooms of a structure, that there are things hiding in the walls that greatly impact signal transmission.
One of the worst things is to have a common wall between a kitchen and a bathroom between your router and computer. These walls typically have a lot of pipes and wires in one small area.
Also, central heating and air conditioning ductwork can block signals quite effectively.
Also, there are a lot of devices out there that share similar/same frequencies
as the wifi.
If you have things like wireless phones, baby monitiors, security cameras as well as close neighbors with wifi computere or video games, the spectrum being used by your wifi link could be very crowed. The technology is amazing and can do a lot of error correction and retransmission such that you can send data through a lot of rf noise. But, it can only do just so much.
An item does not have to be intended to operate on the same frequencies to interfere. It can be defective or a poor design and have signals splattering all over the spectrum. Think in terms of some of the cheap Chinese junk that is out there. The original design may have been certified for compliance but that has little to do with what actually ends up shipping.
Many of the "signal strength" indicators on computers are not really showing you the strength of the RF signal, they are showing you the effectiveness of the communication link, taking into account factors such as retransmission of packets.
Try setting your system up to use different channels on the wifi. Never use the default settings...all your neighbors are probably using those.
If you have a WII (?) wireless video game setup, make certain that it and your computer are using different channels.
Also, things may get pretty slow if you do not use security and have a neighbor tapping into your router.
If all else fails, there are after market antennas that can be connected to your router and pointed to the area where you most often use your laptop.
There are also wireless bridge type coverage extenders that pick up your signal from your router and retransmit it to your computer. This will typically cut your wifi bandwidth in half though. But truthfully, most users rarely max out the bandwidth of their link.
Also, there are new cards and routers that don't just use the B and G bands on wifi. So if your area just has too much RF in the normal bands used by wifi, there are others that might work better. They typically do not have as good a range as "B" and "G" but, if your problem is actually RF congestion, they may get you much better results. I think that the cards that are labeled "N" are just faster using the same frequencies. The ones that I am talking about are "A"... I think.