hmm, I would recommend a case where there's a fan in the front where the hdd's are, or if it's a decade old, how bout just buying a new hard drive , I think new one would probably take less heat than old ones

and also if it's a server computer, then probably better cooling sytems

hmm how about water cooling?
[quote=bobcbar;#3557906;1272788225]I would be more worried about the CPU or hard drive overheating than a the dust
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I agree

hmm, when I had a problem similar to this I think a year ago, what I did was just relocate the harddrive, the location can at least help a bit
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[quote=Ephemeral;#3558080;1272794599]The computer already has 6 fans.[/quote]
hmm, just checking... is the airflow right? and also the location of the cpu