i'm no expert zoe, but i've managed to set up my home network. but then i wrote down my WEP key

if you put the address of the router into your first laptop, you may be able to change the WEP key. the address id probably 192.168.0.1 - save that as a favourite as well write down the new pass phrase and WEP key. i keep them in the box up the loft, and also elsewhere. i also saved them in a text file on each computer (maybe not the most secure thing) so that i always have them to copy and paste.

a MAC address is just a way of identifiying each bit of equipment connected to the router.

what software are yu using to try and connect the new laptop? just the windows software?