Problems connecting a Vista PC to an Airport Base Station
The main reasons people running Windows Vista have problems connecting to an Airport base station are...
Laptop Wireless Switch is not turned on...
Most Windows laptops with built-in wireless have a physical switch which allows them to turn the wireless on and off in order to save battery power.
Ensure that the switch is in the on position.
Airport Extreme base station channel is on "Automatic"
A few people are having problems in connecting their Windows Vista PCs and laptops to an Airport network being run by the new 802.11n Airport Extreme wireless router, notably in the UK and in Europe.
Even after troubleshooting and sometimes even removing all wireless security they still can't connect.
It would appear that the problem lies with the channel which is being used by the Airport Extreme base station.
802.11b/g covers 14 channels, in the US, 802.11 networks can only use channels 1-11. here in the UK (and most of Europe) we can use channels 1-13. In Japan they can use all 14 channels.
Apple Airport base stations and Apple computers sold in the UK can use channels 1-13, those sold in the US can only use channels 1-11.
A lot of non-Apple laptops and wireless adapters sold in the UK are not reconfigured so can only access channels 1-11 despite legally been able to access all 13 channels.
Apple"s Airport default channel on the Airport Extreme base station is usually set to Automatic, what this means is that the base station will decide which is the best channel for the network to operate on. It will see what channels are free and "pick" the channel with the least interference. As other wireless routers default to channel 6 (or channel 1) it makes sense (from a Mac perspective) for the Airport to pick channel 13 as this will result in the least interference and therefore maximum throughput - if there are neighbouring wireless networks. As all Macs can connect on channel 13 and "in theory" all wireless adapters sold in the UK can access channel 13, it does make a weird kind of sense.
So on some occassions (depending on your local environment) the Airport base station sets itself to channel 13 as the ideal channel. As a result some laptops (and some wireless PCI cards) can not access the Airport network.
The solution is to change the channel on the Airport base station from Automatic to a channel between 1 and 11, channel 1 should be fine.
In wrong mode...
If you have the new 802.11n Airport Extreme it is possible to be in the wrong mode, in other words running in 802.11n or 802.11a and your Windows laptop can only access 802.11b or 802.11g networks. Check the wireless radio mode of the Airport base station.
You think you're in the right mode, but in fact you are in the wrong mode...
If you are using 802.11g radio mode on your Airport Extreme (or Express) wireless network and using WPA/WPA2 encryption you may find that some Windows Laptops (my experience is with the Intel 2200BG wireless chipset) will fail to connect to an pure 802.11g WPA/WPA2 wireless network.
If you switch to the 802.11b/g compatible mode (and continue to use WPA/WPA2 encryption) you may find that your Windows laptop can now connect.
I have not checked or confirmed that this is the case with Windows Vista, but in terms of troubleshooting it is something to try.
WEP Key in plain text and not HEX (or not "correct" length)
Though it is recommended that you use WPA or WPA2 some people are still using WEP due to legacy devices on their network.
As a result there are potential problems with using WEP.
One of the problems with WEP is that the actual standard relies on a 10 character HEX key for 40bit WEP and a 26 character HEX key for 128bit WEP.
In order to make things easier for people, vendors use certain algorithms to convert simple alphanumeric passwords (or passphrases) into HEX keys, thus enabling people to use simple memorable WEP password rather than lengthy HEX keys.
The problem is that different vendors use different algorithms to generate the HEX key and therefore a ASCII password on an AEBS will be hashed differently on a Netgear client and vice versa.
One thing is a 13 character 128 bit WEP password will be hashed by all vendors in the same way (if you use 40bit WEP then a 5 character password is required).
Though sometimes not even that works and the HEX key must be used regardless.
Remember that the WEP key will depend on the level on encryption been used, and if you are using 128 bit that the key will be a 26 digit hexadecimal number and not the plain text you used in the AEBS, unless the plain text password is 13 characters.
If you are using 64 bit encryption, requiring either a ten character HEX key (or 5 character plain text password) then you may want to upgrade to 128bit as there have been some reported issues with connecting a PC to a 64 bit encrypted AEBS.
If you enable WEP on the AEBS, you need to note down the Hex Airport Network Password, if you are using 128bit encryption this will be a 26 characters. If you open the Airport Admin Utility, you need to click a button called Password depending on which version of firmware you are using.
The Wireless ASCII Equivalent Password is the plain text network password you use to access your Airport network with a Mac. An example plain text password could be: airportpassword. For 128bit WEP networks you should choose a 13 character ASCII password this in theory is hashed in the same way by all vendors.
The Wireless Hex Equivalent Password is the hex version of the plain text, and this is what you would use with your PC. An example HEX password could be: BAC34DAAAB56B7CADA336B23DA
Using WPA or WPA2
Though Windows Vista supports WPA and WPA2 encryption not all wireless hardware does, especially if it is older hardware. Check that your hardware actually supports the use of WPA or WPA2. You may need to download a firmware upgrade or new drivers for your wireless hardware. Check the website of the manufacturer of your wireless hardware or laptop.
For some reason Windows allows you to bridge your connections (wired, IEEE 1394 and wireless) and this will stop your Windows PC from being able to get a valid IP address. From the Network Connections window delete all Network Bridges.