Wireless Printing/ WEP Key issue

I've bought a wireless printer and whilst trying to set it up it asked for my WEP key for my router, I entered what I thought it was and it was having none of it. So I thought I would type in my IP address into IE and get it that way, but that doesn't accept my username and password that I've been given! And now I'm stuck, can anyone tell me either how to find or change my WEP key or some other solution to get my printer working wirelessly?

Thanks in advance!

 

I've solved this now, by reinstalling my router, which then told me my WEP key!