Compaq presario 2500 battery calibration

Question

hi, i have a problem with my compaq presario 2500..when i boot up my laptop the battery calibration always shows up and when i press C for calibration nothing happens.even if i skip nothing happens..i cant boot.i cant go to the bios..what can i do..my fan and hardisk running.even if i remove my battery calibration is always shows up.i dont know what to do on these.please i need your help guys..thanks a lot in advance.