Vista - Slow internet & un-encrypted network

I have a zoom x6 adsl wireless moedm/router. When my xp box was still alive, i setup my network with encryption that required a word or phrase to log into it (I guess I don't remember which - i think it was WEP-128k). Well, the xp box expired and my new vista laptop doesn't like that configuration; it would not accept the paraphrase or any of the hex-numbers. When I switched to no security, it works np. I would sure like to secure it - any ideas?

I also got a hand me down xp desktop that finds the network no problem, but when it does connect, the network comes to a crawl. Either computer running alone work fine - any ideas about that?

Thanks in advance