Sporadic wireless connection

Background - First setup wireless network 3 or 4 yrs ago using NetGear wireless router,  Because it was close, the desktop PC (Inspiron 530 running XP) was hardwired to the router and a laptop used the wireless connection.  Even though the desktop was hardwired, the taskbar showed that a wireless connection was available.  Then we relocated and because of house layout, the desktop need to have a wireless connection as well.

That was when things got a little wacky.  The laptop didn't miss a beat and it was time to connect the desktop.  It seemed to me that the wireless card in the desktop should see the wireless connection and all would be well.  For the first couple of days I got no connection at all and then suddenly, the desktop was connected for about 12 hours.  The connection dropped from the desktop for the next 3 days.  Thinking that it might be a distance problem, I  purchased a new wireless router and set it up.  The laptop and a smart phone picked up the new network right away.  For 7 days, the desktop never saw anything.  Either there was "no network in range" or "Windows cannot configure this wireless connection....make sure your network card is switched on"    The  Device Manager showed no problems with the card.  Clicking on Properties, the display showed the device working properly and that it was enabled.  I also placed the laptop (running Vista) next to the desktop and it showed "excellent signal strength (5 bars)".

Then last night, the desktop said there was a network in range.  Unfortunately, this network appeared to be one of the neighbors.  The wireless network I had set up was not listed as available.  The other network dropped out after about 10 minutes and nothing was been seen since.

BTW, I have taken the wireless card out of the power management scheme and it has made no difference.

Ideas, please