Wireless n 150 router, pin worked for two laptops, third laptop keeps saying invalid pin/password but i am using the exact same one i used for the other two, anyone know why?

Connect to it directly using a LAN cat 5 cable, not wireless.
Log in as admin to the router, and change the wireless password to something new.
Disconnect the cable then try connecting from each laptop by wireless, when it prompts for password enter the new password.

Connect a LAN cable from the D-Link to your laptop/computer's LAN port, open the browser on your laptop/computer and enter the D-Link's configuration URL..
http://192.168.0.1
The default login = admin
The default PW = blank (just press Enter)
You can now change the default admin password.
You can now configure the wireless settings. (SSID, WPA or WPA2 encryption to protect your wireless network and Internet from unauthorized access).
Now configure the wireless card in your computer/laptop with the router's wireless settings.
To secure your wireless network from unauthorized access, please click on this link and follow my instructions :-
http://www.fixya.com/support/r3559128-wireless_router_security

Chances are that it is still remembering an old password somewhere in the properties... dig through the options an properties to see if there is a place to enter a password that may be overriding the one you are entering when you try to connect.

I know it sounds wrong, but I've run into this before on Windows 7 laptops and have found a previous password embedded in the properties that (once the correct password is entered there) solves the problem.

To connectyour computer to a wireless router, you click the Refresh networklist, then Choose your wireless network and then click Connectto your secured Wireless Network, it will asks for a Network Keybefore allowing you to connect into your wireless network. This NetworkKey is either the WEP, or WPA or WPA2 Encryption key that is used toconfigure the Wireless Router. The Passphrase is an alternate way tosetup the Encryption key.
When you are requested for a Network Key, you can just enter the Passphrasethat was used to configure the Encryption key in the wireless router.http://www.fixya.com/support/r5270415-network_password_network_addressFor information on securing your wireless network,configuring the wireless router and configuring the wireless card in thelaptop/computer, please click on this link and follow my instructions :-http://www.fixya.com/support/r3559128-wireless_router_security

The router's password is a Passphrase or the WEP or WPA orWPA2 encryption key. The Passphrase generates the WEP or WPA or WPA2 encryptionkey and this is in the router's wireless settings. To connect to your wireless router, it needs the router'swireless settings configured ie SSID, WPA or WPA2 encryption key and also thewireless cards in all the laptops and or computers needs to be configured withthese router's wireless settings. Then the laptops and desktop computers cancommunicate with your wireless router.

Router paswords are chase and space senitive, Reset the router and choose a different password that not been used. then repower the router, and connect using the new password.

Your laptop has the old password for your wireless router stored in it...it will depend on your version of windows as to how you can delete the old settings...usually you can right click on the wireless network icon on the bottom right of your task bar to view available wireless networks and go from there...if may be able to select "repair" there and enter the new password for the wireless router

VISTA and wireless don't go well together. First, I would disable your firewall, you can turn it on later when everything works and play with the settings, second use the hex value instead of the password key when logging into the wireless device, third try it both with windows managing the connection and with the vendor software. Some wireless prefer one or the other depending on their compatibility with the Vista virus.

Does your wireless router supply DNS addresses via DHCP or are they configured into the wireless adapter on the other computer? If the DNS addresses are configured into the working laptop's wireless adapter and not the router -- they may need to be configured into the wireless adapter of the new laptop. Is there a proxy server configured into the browser of the new machine that should not be there or does not match the working machine? Is the new laptop statically configured to an inappropriate IP address or gateway or DNS servers for the network you are attempting to use it on.