Ok I have a pc which connects to internet through network card + router.

My wife has got a new laptop through work, it has wireless capability. How can I connect it to my pc to connect to the internet - I want to use my pc as a server.

The router ISN'T wireless.

If the notebook has a network port (RJ-45 connection, looks like a larger phone plug), you could get a CAT-5 network cable and hardwire connect it to the router.

Otherwise, you'll want to get a wireless router.

You can do it the cheap way or the good way ;-)
The cheap way is the way described of Dngrsone here.
If your laptop don't have a networking card you can also buy a networking card which you plug into the PCMCIA slot, - I am SURE there is one. The PCMCIA card doesn'r really come so cheap, so it's also an option to buy an USB 2 LAN converter. I am also SURE you have an USB port on the laptop.

The "good way" is a cordless router. That gives you the flexibility to sit outside your house with the laptop and still be connected to the Internet unless you live in the 5th floor and have a concrete house. Then you may have a signal problem.

But since your laptop has wireless capability you most probably have a an onboard networking card, and yhen you just buy a CAT5 cable. You are then "stuck" by your desk, but it's safe and cheap:-)

You could buy a simple Wireless Access Point (WAP) and connect it with a Cat5e cable to your existing router. (Effectively turning your router into a wireless router.) This will give your PC and the laptop independent access to the internet and will also allow you to share files, folders and resources just as though the PC and laptop were (wire) networked together. You should check your ISP's website to confirm they allow multiple PC's to connect (apparently some plans do not) and if there are any special configuration settings for the laptop. Also remember to turn on wireless security to prevent neighbours getting free internet access over your bandwidth.

What kind of WAP to get? Obviously it should match the laptop wireless interface - look for specs like "802.11b".
Most laptops will be 802.11g which is backward compatible with b so a b/g WAP will suit. If by good fortune your laptop has a "pre-n" wireless interface (which has longer range, less prone to interference etc.) then you can get a "pre-n" WAP. These usually have different names depending on the brand e.g. Netgear calls it RangeMax, D-Link calls it Super G. Note the real "n" standard is not out yet so it's best to match the manufacturer as well because you don't get any benefit if you mix'n'match.

hth