Can not connect to new router, help please

I have an inspiron 1000 with windows XP using a Dell wireless 1350 wlan pc card.  I just purchased an ASUS RT- AC66U wireless router and can not get this computer to connect to the router.  The computer "sees" the router but will not connect.  ASUS was pretty much unhelpful and said it is my problem.  The router appears to be stronger and faster than my old router which was what I was looking for but if I can not use my computer wireless, it is not much good.  It connected flawlessly to my old ROCU (09 model), to my smart phone, (09) model, and my work computer using windows 7.

I was told by ASUS that this router and computer should work together but that one had to have a lot of knowledge to make this happen.  I sure don't have that knowledge.

Any help would be greatly appreciated.

Thanks