I have Compaq presario CQ42-268TX , and everytime when I unplugged the adapter from my laptop, its performance become slower, very bad though the battery power balance still have 89%. My friend ask me to concern to the power plan (maybe I've setting it up not to default). And now, when I boot up my laptop, I need to plugged it with adapter (another power source). Sometimes, my laptop becomes useless when I used to make it portable, bring it outside my house (mall, college, etc) I bought this presario in august, 2010. Don't know what to do, please help me Thank you for helping. Sorry for my bad english.