Alt key is not working

Hello,
I am having problem in using Alt key in Tally and MS office.

Earlier when I was facing this problem I reinstalled the Win Xp Sp2
This resolved my prblem but not again I am facing the same problem.

ALT & CLT both keys are not working

in in Tally : I cant use ALT+C
same way in Excel : I cant use CLT+C , CLT+V


PLEASE HELP ME TO RESOLVE THE SAME

Regards

Chandrakant