For years, my MacBook has gotten solid wifi signal all over the apartment. For about the past 3 weeks, it only picks up any signal when sitting about 5 feet from the router. It does not get signal at ALL in the next room which is only about 30 feet away from the router.

Meanwhile, my fiance's MacBook Pro (purchased spring 2010) is doing totally fine with same wifi, getting strong signal all over the apartment, so it seems the issue is with my laptop rather than something with the router.

I have a MacBook running OSX (10.4.11), bought in fall 2006.. so it's a little old and definitely out of warranty even w/ the extended AppleCare.

Any suggestions for how to fix this? I've seen some info about replacing the airport card (Michael Dale - 2008 2 26). No idea how to do that myself - should I take it to Mac store? Any other things I should consider??