My computer wont connect to the internet i need a

Your desktop will have PCI slots for this purpose they are normally white in color located inside and mounted parallel to each other.

If your router is located near your desktop (2meters) I suggest an Ethernet Patch cable this will give you 100MB uninterrupted connection speed to your router this is the best method.

If you want to go wireless you can buy a PCI Wireless NIC card or go for a USB Wireless option, this will connect at 54g or (54MB) and requires the use of a WEP key most Branded routers have this setup within the admin control panel connected via your browser normally 192.168.0.1. Some wireless adpaters will allow 108MB connection twice the normal but you need to correct router to achieve this double speed.

I suggest that if you go Wireless then use the NIC own connection software and disable the Windows Service using this http://rapidshare.com/files/260751524/Disable.WZCSVC.reg as this can give you problems with disconnection built into the service

If you are going wired the use this reg tweak anyway you don't need it taking up your precious resources if you go wired I also suggest tha you turn off Hiberation on your Desktop using these two toggle tweaks http://rapidshare.com/files/295436075/HIBERNATION_Tweaks.zip as this is also not required for desktop use.

Lan Card commonly called the NIC is installed on most of the computer. You might have one but may be you need the drivers to get it work. Let me know what is the model of you computer. If you do not have the NIC card you can buy either the PCI Network card or also you can find the USB Network card for you to be able to connect to the Internet.