setting up wireless network?

[Fumbducker]

Am currently setting up a wireless network in office for 2 computers to work from. We are using the BT1800HG wireless router which is connected via ethernet to my PC and a Netgear Wireless card on the other PC. We use Eclipse Flex Business 1000 broadband. Having no problems with my PC connecting to the service at all (obviously, I am using this forum after all) but cannot get any joy with the other. After having a secure wireless network at home I think I have probably been to presumptious and added network keys. I originally entered a 8 letter word as my key for both PC's but was then advised to change to a 5 letter key as 8 wouldn't be compatible due to encryption. I successfully changed this on my PC in Wireless Network Wizard but cannot change in the other PC. This other PC is not equipped with Wireless Network Wizard, cannot connect to the router through the Ethernet cable and therefore I can't figure out how to change the settings. Can anyone advise how to change the settings on this other PC or to disable the setting and make it an insecure network. The other PC is finding the signal strength (Excellent 54 Mbps), is sending packets but doesn't receive anything.