Power supply is not working on a Compaq Presario laptop

[Hamlet]

I have my own Compaq Presario CQ45-200 Notebook PC at my home. Recently I noticed a strange issues with this computer. It suddenly goes into battery mode even though the power cord is plugged in. There is no power cut and so how can this be possible. I first thought of changing the power cable but the same continues with the new one also. I think this is the problem of my power supply unit. If the power supply is not working on a Compaq Presario what are the other ways to power ON your computer or if possible how to fix the power supply unit problem?

[Wiro]

Before replacing any hardware, I would recommend you to make sure that it is the power supply issue and not something else. Just open you computer and see if there is some dust around your heatsinks, fans (both psu's and cpu's) and if you are sure then also see that the heat sink fan is fully functional. Recheck if your RAM is properly installed.

[Pugsly]

Several ways to check what is causing you the problem. First of all update your BIOS. Then try to check if CMOS is fully functional and operational. Then see if the LED on the power adapter is glowing. If everything goes right then it is the Power supply fault and needs to be replaced.

[Deep23]

It seems to be the power supply is not able to provide you the enough power to allow things to work. How much voltage of power supply you are having? What is your usage? Do you do a lot photo editing or play high end games? This works generally requires lots of memory as well as power current. Upgrade to a higher voltage.