One other thing you can try before purchasing a new crd is download wireless network utility such as netstumbler (In fact your Dell Wireless Utility will work, too).
What you can check is by moving the laptop around, whether you get a decent signal at a particular location.
You may also check whether there are too many Wi-Fi networks on the same channel (typically 1, 6, 11) as your own Wi-Fi network is. If this is the case you may try and change the channel on your Wireless Access Point.
Hope this helps.
Warm regards,
sarang