Here are some tips to help you if you have problems in getting your USB adapters/cards to work:
If Windows XP does not automatically install the drivers for your card/adapter, use the drivers provided by the vendor.
If you did not install the drivers correctly the first time you connected the card to your computer, subsequent connections may cause the card to be unusable. In such situations, go to Control Panel and select Add Hardware. Select "Yes, I have already connected the hardware" and choose the device that is not working. You will then need to update the driver for your card. Be sure to use the driver from the vendor or download its latest driver from the vendor's web site.
If you still have trouble in getting a connection to the wireless network, ensure that the wireless card/adapter is enabled. To verify this, right-click on My Network Places and select Properties. Check that the wireless connection is enabled.
If the wireless network uses WEP for encryption, be sure to enter the WEP key when connecting to the network. If you are using your own wireless network, you can check the WEP key by using the access point's configuration utility (more on this in Section 5.4 earlier in this chapter); otherwise, you need to check with the system administrator for the WEP key.
If you have a wired connection to the Internet as well as a wireless card/adapter, you can disable the wireless card/adapter by right-clicking on My Network Places and selecting Properties. Right-click on the wireless connection and select Disable. This forces Windows XP to use the wired connection exclusively.
If you are having trouble with a USB adapter, power down the computer and the USB hub (if you are using one), restore power, and then restart. This can eliminate certain operating conditions that are preventing the adapter from functioning properly by forcing it to completely reinitialize itself when you reapply power.
If everything appears to be set up correctly, but your network connection frequently drops or slows to a crawl, look for sources of interference. Common sources include microwave ovens and cordless telephones that operate in the 2.4 Ghz range. In general, these will not interfere unless they are very close to your computer or access point, or if they are situated in a direct line of sight (remember that wireless adapters can "see" through walls) between your computer and access point. Also, if you have a whole lot of wireless equipment set up for testing, such as several access points in close proximity, consider relocating them or powering them down when they are not in use. See section 18.104.22.168 in Chapter 3 for an easy way to survey your site for signal strength and quality.