Gaming Can't connect to the Internet through Wifi?

[Rock Raiyu]

I'm have a problem connecting my laptop to the internet via my wireless router. I don't know what is wrong with it, but I've had this problem for a while. Haven't bothered to mess with it till I got my 3DS. I have it hooked up so that my gaming PC can use the router ethernet port. I can connect my 3DS to the internet just fine, I played multiple matches online without any problems. But I can't connect my laptop or my PS3 to it, it keeps saying that it can't obtain the IP. I've tried resetting it twice and that does not work. I looked in my settings, and I can't see anything out of the ordinary.

Sometimes when I reinstall the software it will work again but then after a few hours it will stop working and then I have to repeat the process for it to work again.

So can someone help me out please?