Try another monitor. Try using an HDMI cable to monitor or TV.
When you unplug your PC to take it outside to blow out the dust, bring it back in to the TV and try the HDMI cable to TV as suggested to compare.
Be sure to limit the fan spinning while cleaning as if it spins faster than designed due to the compressed air it may ruin it.
Guard against static shock to components. Don't work on carpet, discharge any body charge by touching case metal before reaching inside.
Regarding the excellent video:
And how about the intake fan, oh and he should have suggested to the owner to add a rear case exhaust fan to control cooling. Most case air take points will get loaded with dust and that wasn't addressed.....ok I feel better now ! lol
As funny as this sounds, both. Use the spray on the stubborn dust and all fans and cooler fins. The rest can be easily handled with a light brush and the hair dryer.
You can approach this any way you want, I find that the filters, fans and fins hold the most dust. Clean them first then clean up the flat surfaces and rest of the case, if you do it the other way around then the fans,fins and filter dust will coat the case.
This is why I purchased a small pancake compressor, this and cleaning the car and handling low and flat tires!
Amazon.com: compressed air: Electronics
Side note:
When the air is released it makes the can very cold....frozen, when this happens you must let the can rest and come back to a warmer state. Having two or more cans speeds the cleaning process and when empty just dispose in a proper fashion.
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