Setting up Wireless access

Hi all. First time user.

I have just reloaded xp into my Inspiron using the Dell disk following the receipt of several viruses.

Having done this, I am at a loss as to how to set up wireless access to the Internet which I had before.

Do I have to load something else? I haven't used the Drivers disk.

All I have done is reload the Virgin Broadband disk. Not even sure thats necessary.

My set up is a Desktop connected to a wireless router from which I would like to access via my laptop as I did before.

Help please.