Up until a few days ago my 5 year old Dell laptop (OS = vista) picked up my home's wireless network fine, but now it's not recognising it. It picks up other networks of my neighbours, but not mine. My other laptop picks up my network just fine so I've been using that in the meantime.
When you say "It picks up other networks of my neighbours, but not mine" do you mean that it can see other networks, but your network is not visible?
If this is the case, it could be worthwhile trying an alternative wireless channel as it may just be a combination of older hardware in the Dell and some new wireless device (either your's or a neighbour's) causing interference.
The primary wireless channels are 1, 6 or 11 for 2.4Ghz when using 40Mhz bandwidth.
It depends on the make/model of the wireless router.
Opening a command prompt from the Accessories Folder, type ipconfig and look for the Default Gateway address (ie 192.168.0.1). Type that in to the address bar of your browser (Firefox, Chrome, IE) and enter the routers username/password.
On the landing page there would be something along the lines of Wireless or Wireless Settings and the channel selection will be in there.