router / wireless network not in sync

hi It's been 3 days I haven't been able to connect to the internet on my laptop. I have a wireless network set up in my house with a router. It was set up about 2-3 months ago and everything was working fine. The desktop computer where the main internet is set up works perfectly fine. My laptop is running on Windows XP (service pack 2…service pack 3 will not install). I always leave it on standby. The router is a D-Link if that helps. when i try connecting, it says "acquiring network address" and after about 2-3 mins of trying to connect to the net, it says "connected with limited or no connectivity" and i obviously can't log on. the icon tells me to click to troubleshoot and it reads: "did not receive IP address" / "wireless adapter failed to get valid IP address. Can be due to authentication failure with the network, incorrect wireless security passwords, or bc of a DHCP server malfunction." Is there something simple that can fix this like maybe uninstalling and re-installing the network or is it something more along the lines of virus or … ? I appreciate any help you can give me and I'm not very technical so be kind ) Thanks!

Hello. If your wireless network has a security passphrase the most likely issue is that the key has been entered wrong. You should disconnect from the network, and then try to reconnect, at which point, depending on what software you have handling your wireless connections, it should ask for you to enter the passphrase. Please make sure it is entered correctly. If you do not know what the passphrase is, or you do not have a passphrase then please respond back with the actual model number of your DLink router.

ok, so i tried that and still nothing. even when i went to the router website, on the back of the router it tells me what to enter for user and password and it said that was wrong lol the router model is: DIR-615