Hi, my acer laptop 7520 shuts itself down after booting for few seconds. It has Vista but dont think its a software / virus issue. As I got into BIOS / booting menu, it did not stay there. it shuts itself down. I removed CD rom from laptop but had same result. It has two 1GB rams, I removed them one at a time but had same result. I then removed Harddisk and tried to make it boot from USB, but had same result. It was shutting down after 10 - 30 seconds. I see the Fan running when ever I start the laptop. Fan is very clean. no dust, dont think its a heating problem then. please can some one advise what could be issue. thanks. I ran it on full battery but had same result. Then I removed battery and connected the power cable into laptop, same result. it shuts down after few seconds.