That's why he's called Grumpy !
Is the router still detected by the old computer -- if there's been a power surge it could have been reset to factory defaults which may include wireless disabled.
Have you checked the router settings for wireless mode -- the new laptop may be a newer standard than the router is set to. Presumably wireless SSID is being broadcast and you haven't enabled Access List.
Do refer to the literature which came with the router or download the manual from the maker's site.