So the other day the WiFi stopped working on my Dell Inspiron 1720 laptop so after a little bit of troubleshooting and assumed the mini-PCI express wireless card was fried and ordered a new one from Dell's website. The new one didn't work either. Then I suddenly remembered that there was some sort of WiFi switch on the side of the laptop. I felt the switch and moved it moved it in the direction of "On" and it clicked! So it had been turned off! We move our laptop around a lot and somehow the switch had been switched to the off position accidentally.
I'm still glad I ordered the wireless card though, as it is a Wireless-N card so now if I upgrade my router to a Wireless-N router I might get faster speeds!
[img_assist|nid=373|title=Dell External WI-FI switch|desc=Mine looks something like this, but not exactly.|link=node|align=left|width=373|height=271]