I have a pentium II 266 overclocked @300-tried for 333 but programs became unstable-I'm confused if whether I should leave the case cover on or off. I find taking it off reduces some heat off my motherboard, but attracted some dust particles on it and a decent amount on the fans of my Card Cooler for my videocard. On the otherhand, leaving the case cover on inhibited the collection of dust but increased the temp. Furthermore, I read something saying that leaving the case cover on promotes proper airflow because of the design of the case. If anyone has any personal experiences or tips please reply, thanks.
Dust really is not a problem unless you let it build up over severals years without cleaning it out of the inside of the case.
I would recommend you run WITH the case ON, but add one or two more high flow fans. Radio Shack sells a 65cfm 120 volt AC fan which you would plug into the wall outlet, or there are 108 cfm 12 volt DC fans available which you plug into the power supply.
I cut a 4 inch hole right above my CPU and mounted a 108 cfm 12 volt DC fan sucking out the top of my case. I then added a 65 cfm 120 volt AC fan as my intake front bottom of the case. I get tons of air flow now for under $30.00
It all depends on which case you have, and what the configuration of your ventilation is. If your case is designed well with proper ventilation, you can actually raise the temperature of your cpu if you remove the case since some were designed well to make the air flow through the case and over the cpu. When you remove the case, it stops the air flow moving in the same way. If you want to know for sure, get a mobo monitoring program, or an actual thermometer and try it both ways to see which is better.
I've been running my OCd PC with the case (side panel) off for about 2 years straight now without any problems whatsoever. It's in the guest bedroom, so I'll put the case back on when people are visiting. I've found it runs 10°C cooler without the case!
On hot days when the AC's off, I'll sit a full-size house fan to blow on the case- I do have overheating problems with ambient temps above 85 after the CPU fan failed a few weeks ago.
I havent got the case on any of mine at the min, and havent had for quite a while they run WAY cooler with it off and the air flows fine as you can aim them straight at the cpu/graphics cards etc. without having to send it round the case.