possible virus, assistance please

[judym]

Looking for a bit of advice; Although my laptop worked fine when I used it a week ago, now it boots up but shuts off within a minute of booting. I'm thinking it may be a virus? (I do a virus update pretty much every day I connect to the net). It does not stay on long enough for me to use the AVG virus program and I have not been able to reboot in safe mode. Would doing a total reformat take care of the problem if it is a virus?
Thanks,
Judy

[mjc]

A more detailed description of the problem, details about the laptop (make/model) any error messages...

[judym]

It is an acer travelmate 4654LMi. Win Professional. The system just goes black with no error message. Prior to rebootting it goes through the scan disk routine, completes this and reboots with no problems, after 45 seconds or so it shuts off.

Judy

[mjc]

Can you access the BIOS?

If so, can the machine sit on the BIOS scren for longer than a minute or two or does it shut down?

How old is this machine? Is it still under warranty?