Each time I log in to my laptop the numlok key is automatically on. I have to shift and hit numloc key to disable, but the next time I log in it is on again.My operating system is Windows XP and my laptop is a IBM thinkpad T series

This is an old problem on IBM Thinkpads. There are a lot of answers, but the easiest is to go to this website and use the little program there.

NumLock Problem - XP

Download it, run it. Check the box to have NumLock ON, clear the box to have numlock OFF ==> then "Apply" the change and you're done.