We had some real "Fun" with the built in wireless network card in my wife's laptop recently. See, the thing started failing for no apparent reason. Then sometime later, anywhere from an hour or two to a day or more, it would come back on and work until the machine was turned off for the night.
I am not a hamster and I'm sure I don't have to tell anyone how ultra aggravating this kind of thing can be. The first thought I had was that the wireless card was bad, so I dug around the HP site and found the part number for the unit needed by this particular presario and proceeded to purchase another one post haste.
It didn't help at all. More digging, trying all the obvious things like re-install the drivers etc. with no results at all. Finally I find mention of the exact same problem on forums... several in fact. Seems that Compaq Presario f500 series notebooks have a problem with their built-in wireless cards. Sometimes they stop working. There was a bios update that got several people going again and I tried that with no results. I was starting to seriously consider getting about 30 feet of CAT6 ethernet cable and setting up a hard line as a temporary measure when I discovered the ideal solution.
Turns out that you can get these really cool Wi-Fi cards housed in something a bit bigger than a flash drive with a USB connector on it. Get that sucker home, install it and poof.. wireless works again thanks to this ingenious little gem from Netgear.
I plan on buying a spare or two sometime just in case.