ok here is johns thoughts.... the fan will be working as most lappys have inbuilt protection and will not startup if they are ermmm fooked... a crevice tool or blowing into the vent will not be enough to get rid of the dust/crap around the fan. the back needs to come off by a professional to be cleaned properly, and best done as soon as to prevent cooking of the cpu. perhaps a swing friendly engineer will do it for you or ask that the engineer cleans it in front of you or will do it at yours on a 'home visit' ( in a vanilla way

) but if the engineer is a professional then they wont even look at the contents of your files as they know we all have private files
another thought is because you are on vista(and in your 8 mins of running time) set a very strong password on your account ie lots of numbers caps and special characters and then add a limited user account that the engineer can use for testing