My laptop has a Mini-PCI Wi-Fi card from Orinoco that I installed

I bet it's the same card as in my laptop. It's also one of those mini-PCI cards.

Is your laptop an Acer by any chance? (though no doubt those cards have ended up in many a laptop series)

For now this hasn't given me any problems. I bet I'm one of the only people for miles around here that actually has wireless ethernet, but I wouldn't be surprised if one of my neighbours one day finds out that he can easily tap into my network. Needless to say, this would be a Bad Thing.
If I can't get WEP to work, I might try using MAC-address restrictions. The USR also supports this.