Jo, for your monitor, just take the vacuum, and vacuum over the vent slots with that sucker on high. It will pull out the worst of the cat fur. I have to do that regularly to my whole machine.
As you you all who have your computers where sawdust and other little particles can get into them, let me tell you a story. When I worked at that part-time, they had a small fire in the store, in an area two departments away from the frame shop. The water got right up to the shop door, and nothing got into the except soot. The computer is outside the shop, under the sales counter, in a fairly protected place. The outside of the tower looked, and felt fairly clean. It didn't need much cleaning. After that, though, it started acting funny. Just every once in a while, it wouuld crash, or drop data, or have a wierd spasm of some kind. The other two folks working there, at the time, are not very comupter literate. I was the resident computer whiz, and I'm not all that whiz. Anyway, I was not in enough to really see what it was doing, and the other two thought that it was operator trouble. I finally got tired of having problems with the thing, and got the three of us together, and started asking questions. Seems that the problems that they were having were much worse than mine. I knew just where to kick the thing. After that, it took almost a month for me to convince Corp to replace the thing. When they finally sent us a new one, I peeked inside the old one. Everything was covered with a fine layer of soot. It was inside the case, and in between the layers of the platters of the hard drive, and on the drive heads. Just enough very tiny particles that,every once in a while, it would hit a particle, and boom, no computer.
The moral of this story, Children, is to keep your computer where it can't get junk into it. Also, to clean the thing, at least once a month, whether you think it needs it or not. Look on it as preventive maintainance, just like you do to the rest of your machines.