You will need to know which Intel wireless adapter is installed before you can download the correct software version. This page will help you identify your adapter - http://www.intel.com/support/wireless/wlan/sb/CS-025417.htm.
Next you will need to download the driver for your Intel wireless adapter by going to http://downloadcenter.intel.com/default.aspx.
1. Select "Wireless Networking" from the Product Family
2. Select "Intel(R) WiFi Products"
3. Select the Intel wireless adapter identified above. If you do not see your adapter listed, you may need to select the "Discontinued Products" button.
4. Select your Operating System (ie Windows XP)
5. Select Drivers
6. Select the file that matches - you may have to scroll down the page a little.
7. Select the file to download - you should download the file that ends with "exe". You will have to scroll down the page to find the file.
8. Scroll all the way down the page and select Accept.
9. Select the link to download the software.
10. There may be an Active X message at the top of your browser. Accept the file to download.
11. Select Save and save the file to your desktop.
12. Go to your desktop and double-click on the file to install the driver.
Good luck! This should fix your issue. Please contact Intel Customer Support if you continue to have issues and an agent will assist you. You can find the phone number for support at http://www.intel.com/support/feedback.htm.
Intel Customer Support