Excel version: 2003
Symtpoms:
Whenever I input 1, excel automatically change it to 00.1.
Whenever I paste a value with a comma (",") as a deliminator, excel
automatically split it into two cells and remove the comma.

Possible cause:
The whole problem starts when I tried to split values in a column with comma
deliminators. It seems that Excel remembers this action. I have not found a
way to remove this hidden action.

What I have tried:
I have tried Tools-Options-Calculation, set Calculation on "Manual". It
has not solved the problem.