OK: let's see what can be done.
Do we know yet whether the problem is the Vista machine not "seeing" a working wireless access point, or the wireless access point not working, or the wireless access point working but not "seeing" the router (and through it the internet).
First, are you sure the wireless access point is connected to the router and working? Do you have any other wireless device that can "look for" it? Can that wireless device get a DHCP address from it? [You'll probably want to secure it later, but let's get it working first.]
If you can't "see" the wireless access point from another wireless device, do you have a PC that can connect direct (wired) to the router? If so, use that to see if the wireless access point is recognised by the router. It should have its own DHCP address that the router will know (or the instruction manual will tell you what it is).
With the answer to those questions, we can move on to the next stage of diagnosis.