A wireless signal is convenient because it reduces the number of messy wires and cables connecting things. A bad wireless signal, however, can really mess up your browsing: Pages won't load, connections get dropped and browsing slows down. Bad reception can cause all of these things, but if you are getting your wireless connection through a PCI adaptor, you can resort to a few fixes to overcome your reception problems.
Bring up the Windows Device Manager on your computer (how you do so depends on the version of Windows you have installed, but generally you can access this feature through the Control Panel). Choose "Network Adapters" and double-click the adaptor. Go to the "Advanced" tab. You should see an option to change the signal strength. Raise it to the maximum. If you see a "Power Save" option, turn it off.
Reposition the wireless modem. Try to keep the modem a clear distance from the wireless PCI adaptor. If possible, position the wireless modem in the middle of the room for an even signal. It's also better to keep the modem away from the computer and other electrical appliances because the electromagnetic radiation they produce will interfere with the signal.
Add a second wireless router if it's not feasible to reposition the modem. If you decide to add another router, try to get the same brand for maximum compatibility, although different brands should also work together.
Use a repeater to increase the reception. A repeater is similar to a second router except it does not require all of that cabling; plug it into a wall socket, and it retransmits the signal, improving reception. This is a good way of doubling the range of the wireless router. With the increased range, the signal can reach the wireless PCI adaptor more effectively.
Use a Wi-Fi antenna. Wi-Fi antennas help reception by focusing the wireless signal in a specific direction, rather than spreading it around a general area. This is the best method for increasing signal strength through walls or floors. Although this is a good way to increase reception, not all adaptors work with an antenna. Consult the documentation for the adaptor to see if it has this functionality.
Turning off the "Power Save" option as mentioned in Step 1 will increase not only signal reception, but also power consumption. You can leave this option on if you are concerned about energy use.
Be careful while making adjustments through the Device Manager. Settings made on the "Advanced" tab can mess up the adaptor if done incorrectly, so only change what's necessary.