HELP.
I have a user who has 2 laptops (Compaq CQ61s), one will connect to their wireless router (Zyxel P660,) one wont.
They are slightly different spec, but basically the same.
Both running Windows 7.
The router has been factory reset and still not connecting, it can see it, but it just refuses to connect.
Its ok on other wireless connections. I've even checked to make sure the router is broadcasting on the least congested channel in the area.
Any ideas please?

MAC Address filtering on the router?

Clubber – not if it has been factory reset.

EDIT: removed question already answered in OP 😳

Are both laptops capable of 802.11 b/g wireless ?

It seems that there are a bunch of different Zyxel P-660 routers – what is the exact model number that you have ?

Yep, both laptops to same spec (same model) although the "older one" is dual core with more RAM, whereas the "newer one" is single core and less RAM.
Cant remember off the top of my head, need to check in the morning. P660 HW-D1 i think
I cant see it being a router issue as nothing would connect, surely?
The router has wpa-psk wireless encryption.
Thinking about it, the one thing i didnt try was to turn off the wireless encryption and try and connect to it as an open network.

while you are at it try giving it a fixed IP address as well. Sometimes they connect but don't pick up an ip address so it looks as though they haven't connected

I assume it isn't the sort of router you have to hold down a button on the router in order for it to accept new devices?

Might help if you posted your ipconfig /all?

Start -> Run -> "cmd" [Enter] -> ipconfig /all [Enter]

Check the laptop that doesn't connect for
1) TCP/IP is using DHCP
2) Start->run->cmd[enter] ipconfig /flushdns
3) You can see the SSID – shoudl prompt for key
4) Check loacl firewall settings to see if the new 'network' needs to be added into a trusted zone or somethign odd like that. Can sometimes be useful to add the whole subnet of the DHCP scope for example 192.168.0.0 with a 255.255.0.0 mask or it could be 10.88.0.0 or whatever range the router wants to assign.

Dud wireless card? My PC did this, other times it would connect but have a really laggy connection.

Its a Zyxel P660 HW-61 router
1) yes
2) not tried
3) yes and yes
4) Switched firewall off and still the same.

Static IP address?

Nope, no static IPs on the LAN (PC or router)

No offence and all, but I do wish people wouldn't keep recommending static IP addresses as a 'fix', it causes me no end of headaches when it bleeds onto corporate networks and I've got to spend half the afternoon trying to find it.

Stuff like this is hard to diagnose without being in front of the machine, WiFi can be a complete pain. I'd look to disabling WPA temporarily as a diagnostic step (one less thing to worry about) and I'd question the assumption that "they're both the same" when it's immediately followed up by "apart from these differences". Is one b/g/n and the other b/g only, perhaps?

Are they using Windows to manage the connection, or some proprietary OEM software?

Can you get the laptop to connect to any other wireless networks? Ie, is the problem "it won't talk to this router" or is it "wireless is broken"?

I would suspect the wireless adapter is not compatable with the encryption settings you have in place. As Cougar suggested, disable the encryption and try again.

Might only be compatable with WEP. Newer wireless use WPA.

No offence. It wasn't a recommendation as a fix but rather a route of investigation 🙂

I had a similar problem that was really starting to get frustrating. As always it was a simple fix – I had the encryption type set to TKIP instead of AES.