ok go to

Start
Control Panel
Power Settings

everything seems to be fine.

Battery at 100 % and states that is is plugged in fine.

Any ideas?

overheating

Yes the machine could be overheating.... you say it could happen at random times... how old is your machine? what type of programs do you run. this could be very simply to fix like cleaning out dust.

my machine is about 2 1/2 years old - it was bought from the laptop shop, and was refurbished i think.

always on is msn and skype, avg, googletalk. other programs: word, adobe pdf, firefox, ie, windows media,
i can't remember others, but that is essentially it.

yes very random times today it has been on since 7am.... so that is 12 hours and it hasn't gone off


I din't think i would be able to clean it, is it expensive to get done?