How do I clean my computer from dust?- alternatives

how about a brush and vacuum cleaner with a hose. hairdryer make sure to set it to cold.

Depends how extreme you want to go with it  

is it just the heatsink in particular you're worried about or the whole system?
I wont write an essay if its just the heatsink  
no 'special' equipment is available to my knowledge, or required to be honest, other than a static wristband if you wish, opinions vary on the effectiveness though
I use one on the better safe than sorry principle.
let me know and I'll draw up a cleaning plan/instructions for you
Moto

Leaf blower.  

The whole thing with the heatsink.

For seriously dusty systems I've used an air compressor and vacuum cleaner from about 2 feet away - not too much air pressure that might damage anything, and no static from the vacuum.

Works a treat.

Ok,
Grab a toothpick or cocktail stick, an old toothbrush, small phillips screwdriver, plenty of kitchen towels and your vacuum cleaner.

turn pc off obviously  
unplug cpu fan and and remove it from heatsink ,
use the toothbrush to brush the blades and the toothpick to get any welded on gunk off, once clean put your fingers on the middle of the fan and gently but firmly push to make sure its sat correctly on the motor housing,
a tiny blob of grease on the bearing doesn't hurt if you can get to it, or a spray of WD40 (lubricating spray) let it dry while you get on with the main heatsink.

Best way imo of cleaning the heatsink is to remove it, wash and dry well then re-apply thermal paste before reassembling and re-seating it.
but assuming you are leaving the heatsink in place,

Disconnect your rear fan (if fitted), just the plug, no need to remove the fan unless your cleaning that too
set your vacuum up so the hose is about 6-10 inches from the pc,(just close enough to have a bit of suction inside the case so it pulls the crap out) and sucking through the rear fans mesh/hole
gently use the toothpick to loosen the fluff/gunk/what the hell is that! from the heatsink, being careful not to knock the heatsink about too much,
now and again turn the pc upside down and let stuff fall onto the kitchen towels
you can use a rolled/flattened piece of paper to get further into the Hs if the design is a bit much for the toothpick,
once your happy with the state of it, do a final de-gunk inside the case, replace your fan *Remember to plug it back in*
and repeat as necessary whenever you need/want to,
hope this helps man,
Moto

I did it with a hairdryer, I didn't remove the heatsink, I just unscrewed the fan becuase I was scared of removing or ruining the thermal paste,
When I turned on the hairdryer dust blew into my face and I still have itchy eyes and sneezing.

I also installed a GT 240 while I was at at it.

My computer is as good as new now, the only thing out dated is the Pentium D 925, I plan for an upgrade soon.

I used pretty much all of your advice, the vacuum cleaner, the hairdryer, toothpicks and everything, EXCEPT the leaf blower.

CPU idle drop from 50-60 Celsius to 36-40!

Anyways these probably are the best alternatives to dust cleaning your PC.

This is a MINT thread, perfect.

BTW, I'm new to this website; how do I mark it as SOLVED?

The reason you remove the fan is so you dont make it revolve and feed current back into the mobo potentially blowing it,
to select a best answer and mark the thread solved, you have to have started this as a question with answer thread, then there should be an icon by everyones names for you to click which you think was best,
dont worry if you made a 'wrong' thread, just remember for next time  
Moto

So a discussion is never solved and goes on forever?

Yup, until a Moderator sees that its been inactive for some time,
then they will close it, I suppose you could request it in your next message and one may be nice and close for you  
Moto

Ok here goes,
Almighty moderators, may you close this thread?

LOL first select the best answer....  

i exclusively use air compressor and have never damaged a computer.

I just +1ned everything.

if there is no cans of compressed air in the UAE,
go on-line shopping ebay or amazon and buy a home delivery..

This topic has been closed by Hunter315