Could not connect wifi

Hello,
In my apartment every floor has different wifi connections. I could not connect to 1st floor (my floor) connection - it shows signal strength Good or Very Good but always says "Acquiring Network" and then "Limited or No Connectivity". My laptop IBM thinkpad (XP Professional) was able to connect to 2nd floor network, however it is weak and very often disrupts. I tried to give a static IP (i dont know the concept, just like that I typed some digits) then it says connected but no page is opening. Can you help me please.

Thanks
Ram