Battery trouble in laptop..

[Ganoosh]

I have a compaq presario v5000 series and it wont start anymore I have a new ac adapter for it an i know it works but is there a sure fire way to know if it is the battery that needs replacement or is there a way to fix this problem.......when i have the battery in and the ac adapter on the lightning sign blinks when holding down the power button please someone help me with thsi issue and let me know if i have to fork out 150$ for a new battery thank you

[Ganoosh]

something else i forgot before this prblem happened the laptop would shutoff I think due to battery overheating

[hardball]

does the pc work when it is running off the adapter?

[Ganoosh]

does the pc work when it is running off the adapter?

No it does not i think it needs the battery as a power-up or its the connector for the startup proccess