my dell inspiron restarts without any reason. Only thing noticeable is fan, at its peaks before shut down. it looks like heat up issue due to clotted passageways, and if it is how can I clean up my laptop's radiator ?
Power it off. Remove battery, take off mains (AC) power. Press power button a few times to make sure there's no significant energy stored somewhere.
I recommend compressed air, the canned version (that retailers won't sell to minors in the United States.)
If you must, use a vacuum cleaner in reverse...make sure you can vouch for the quality of air, though. You don't want to be blowing more dust in the thing.
Never use a compressed air hose from a Gas Station / Service station. That air is not clean and you will be blowing some very nasty things into your laptop, such as small fragments of metal.
Video tutorial here.
Dell guide here.
Basically, undo the cover plate with the screws shown:
Undo the 5 screws to take out the thermal transfer thingy. The black end part (2) is a filter. It is tricky and mostly unnecessary to get to the fan itself. I've found that the compressed air is unnecessary as the filter does a great job of collecting stuff. I live with a hairy dog and removed lots of hair from the filter and found the fan blades fairly free.