Revisions for Willow's wireless problem

Hey all,

Ive got a technical computer problem and was wondering if anybody could help me out.

Last year i had a desktop computer built for me. At the time they asked if i wanted the computer to be able to have wireless in which i said no because i was staying alone in a unit with cable connection.

Nine months later and now that ive moved into another place the computer there is on cable and i have no option but to work off the router.

Problem is my desktop does not have wireless to work off router.

Should i go back to the person who built my computer and ask if he could make it wireless or is there an easier way to do it and how much costs would i incur if im to buy stuff to make it wireless.

Im a uni student with a low budget so cheap, efficient way works for me. Additionally im not very techincal when it comes to IT terms so layman does it for me.

The specifications of the computer built for me is below (cut and paste btw):

Intel S775 Core 2 Duo E8400 3.0GHz CPU
ASUS S775 P5K-PRO Core 2 Motherboard
DDR2 2GB Corsair 800MHz PC6400 RAM TwinX Kit
320GB Western Digital KS 7200rpm 16M SATA HDD
ASUS 8800GS 384M PCIe Video Card
22” (55cm) LG W2242T-BF LCD Monitor
Antec Three Hundred Case (No PS)
Corsair TX750W 750W Power Supply
Microsoft Multimedia keyboard Black
Microsoft SideWinder mouse
LG 20x DVD Burner SATA Black OEM
Logitech R-20 Speaker System
MS Windows Vista Home Premium 32bit OEM

Any suggestions of what needs to be done to make my computer wireless is appreciated.