I just got an ac adapter for a computer one of my friends had given me, not that old a Sony Vaio pentium 4, windows xp so it's not completely dated. The computer hasn't been on in probably over 9 months because the ac adapter broke and she never wanted to get another one. I plugged in the adapter, lights up on the adapter box but I'm getting no response at all from the computer. Is it possible the battery just needs to charge for a while because it's been off so long? If so how long should I charge it for before I figure it's something else?

CMOS battery will not prevent the Sony from booting, but it will give error codes than shut down. CMOS battery is needed for BIOS loading and for date.

all sony laptops have very intelligent EC\KBC chip. the firmware of this chip is logging any errors during laptop "life". when the critical sum of these errors occurs, laptop won't turn on(again, this is unconfirmed empirical data, but my statistical data confirms it)

raybay, there's difference between BIOS data and CMOS data. CMOS data are never stored in BIOS chip.