Hello, At work I'm using a mac pro (3months old now). I was working with the older model (powerpc) before and was very happy with it. However the intel based cpu would fullfill more needs for the internal-used-windows written- programs. The intel-mac is under my open desk, just where the earlier one was 1 year ago, doing the same and exact things... Two months ago the mac pro seemed to act strange. Ventilator (fan) seemed to spin like hell. Thought it was just because of heavy use (CS3 stuff). After a while it began more frequently and out of the blue. The wind it produces isn't even warm. I contacted the firm from which I bought, where they told me to do some tests while booting the MAC install disk. There I did a full system check without any "errors". I did all the updates as well as the one to be known to resolve fan issues. Still without a chance. I emailed the log (which they asked), and the told me to reset the MTU or something. (disconnecting everything for few minutes, restarting with only keyboard + mouse). Didn't resolved anything... The only thing to let it stop: shut down and restart (only a cold boot works, restarting doesn't let the fans stop otherwise). Remark that the heavy fan noise, is even heavier than the ones on the tests. It keeps making noise till I put it off. Mac os X can be closed down normally. It once must have remained to blow for like 10 minutes. People were going crazy around me because of the noise. It happens time to time. I had a week > 2 times a day, fans started spinning. Today it happened after 30 minutes when I booted the mac (last time before was a week ago). It looks very strange to me. Today I contacted the firm again. Friday evening I'm bringing it in. If it is a hardware problem it will fall in guarantue, otherwise (software problem), It's paytime :S. So far for the service... Is there anyway to look to know for sure it's not software related? But then again I can't think of a program I used in the first 30 minutes today which caused the fans to spin... (suitcase, mail, iCal, firefox, safari, parallels,neo-office,... looks all very common to me) Are there any known things to be aware of or to keep in mind. thanks in advance! ps: I'm still a mac-dummy. I'm considering buying a mac for home as well to learn more about the machine. Any help for learning more (error reports, general ideas, tutorials,...) is well appreciated. I will keep an eye on this helpfull site as well! TOP! ps2: Not sure if this is related to MAC pro or mac basic fora. Since I don't call myself an expert I posted in here. Sorry if I thought wrong... As of today my roots refer to "windows", my future will embrace mac.