If it's that bad, you also need to regularly clean the inside of your PC, especially the fins of the various heatsinks (the big one under the fan on the CPU, the graphics card, the motherboard hubs, etc. For this I use compressed air cans and hold the vacuum cleaner nozzle in the vicinity to suck up the dust you've unsettled with the compressed air. If you look at the fins on the CPU, it's amazing how much dust is trapped in there. This reduces the heat escape from the CPU, and therefore increases the CPU running temperature. Also pay attention to the circuit boards, brushing with a soft brush (I use a 1 inch pure bristle pain brush (never been used for painting!)). Dust can build up on boards and over time may cause a conductance between adjacent tracks of the buses.
To do all this, turn all power off, but if possible, use an earth strap on your wrist and connect to the chassis of the machine. This assumes the chassis of the machine is earthed. If you disconnected from the power supply, it won't be, so if you want to be really precise about this, set up a "dummy" power lead which has only the earth connected (not the live/neutral feeds) and connect this to the machine for the operation. (The lead is otherwise connected to the wall socket as normal, but only for the earth connection. If you're in any way dubious about electrics at this level, leave this bit out, but be careful what you touch in the PC.
Re - static - that dust has to go somewhere, so why not have a static charged surface somewhere to attract it? ... probably not that practical!
Re - compressed air canisters. This part of the operation may cause some liquified accelerant to be expelled from the canister. This is Ok, but leave it a few minuted to completely vapourize and dry before turning the PC back on.
Hope that helps
jdf
EDIT - actually - thinking about it - that's probably not liquified accelerant, it's probably natural water vapour in the air condensing on the rapidly cooled, rapidly reduced pressure of the air jet from the canister.