If it's winter with no humdiity in the air, yes.
You can deal with static easily by putting one hand or your elbow on the power supply.
Compressed air. It comes in a can. You can buy it at places like Staples and Best Buy
I have use vacum to blow out mine and clean the rest with rubbing alcohol as it dries fast and won't mess up your computer.
For the outside, you can use whatever you want. For the inside use compressed air but be careful not to unplug anything or disconnect any parts of the components
for keyboards use natural bristle brush (the more expensive ones) not plastic, that will create static electricity, and rubbing alcohol to brush out dirty keuboards and hard to reach cracks and crevices. and yes if your messing with motherboards your supposed to be grounded, the wrist straps have to be then wired to a ground, andyou have to wear labcoat with wire mesh in it that is also grounded, but unless you want to spend more than the computer, don't worry about it. ESD Eletro Static Discharge, like shocking yourself in winter (winter = dryer air, more ESD) whether you feel it or not, our bodies our sending out shocks all the time, these shocks can damage the small circuits and/or soldering joints, and it's not immediate, could cause it to fail later in life, but if you've got an old dirty computer, its too old to worry about, you'll be ok. just don't clean it while rubbing your hair with a balloon...
compressed air is good also!