Hi, first off lets check a few things....
You say that you have wireless and wired... lets concentrate on the wireless...
Every system that connects to a router is identified by a MAC address. Find the MAC address of the system that is not recognizing the network, and see if your router is seeing that system by going to a working system and querying your browser. ( Most home browsers have a default IP address of 192.168.8.1 . Your may be diferrent consult your router documentation) You can view this information by finding the area in your router that identifies "attached devices" or some equivalent
If is not recognized in your router, then make sure the band type is the same (802,1 A,B, or G) (I assume that since it worked before that it does, but this gives you an idea of what to look for when problems occur).
If the router is seeing the MAC address, then we can eliminate that side of the system from problems and concentrate on the laptop.
On most systems, you have an icon in the system tray that indicates you are connected to a network and will give a status symbol as to whether or not is is active, dormant or has a problem. At this point, we are just looking to see if your laptop is recieving a signal from the router.
If there is a signal, then there was an alteration on your laptop of the configuration that connects you to your wireless. This means the card and the network is working fine. So concentrate your efforts on configuring your laptop to recognize the signal it is getting.
If it is not getting a signal, then use the software that came with your wifi card to join the network. It may be necessary to uninstall the software that came with your card, and re-install it to clear out any bugs.
Remeber that if your MAC address is already recognized by the browser, you will not need to authorize it. But some routers (like my NETGEAR814) need authentication to allow an unrecognized MAC address to access the system ( a good security precaution if you ask me)
Once you see the wifi card recieving a signal from the wireless router, and you see the MAC address on the router, you are connected.
From there, you just need to configure you laptop to use the incoming signal. Right click your system tray icon and see what options it offers. You may have to play with getting it to recognize the incoming signal, but at least you are getting the signal through your network, and that is what you asked for help on.