HELP unbootable Mac Pro with crazy Fan!

I recently upgraded my Mac Pro with 24 GB RAM and have filled each bay with 1TB drives. Everything was working great and then all of a sudden it won't boot, had never heard the fan at all prior to this and now it's very loud. There were no warning signs, poor performance or error messages. I tried a different graphics card and discovered I had the latest and had to put the original back in. A tiny piece of plastic that held the prongs in place broke off. I was surprised it still worked in spite of that missing piece of plastic.

Would anyone know if it's a software or hardware problem? Is the problem on my computer or Apple Display? There is no Mac repair near me and I will have to mail it to the nearest one in Makati I suppose. Any advice would be greatly appreciated.

The heat sensor to the Processor tend to go out on the earlier mac pros that will prevent it from booting and that is why your fan will speed up and get louder. Also the heat sensor to the ram will do the same thing, you may have broken one off with the plastic piece you are talking about pull all your ram out and try adding two gig at a time to see if one is bad and don't use the one that is broken. it's worth looking at.

You obviously know more about the hardware than I do. What you say makes sense and I will try your recommendations. Is the heat sensor to the Processor a replaceable item? Or is it part of the motherboard? The piece of plastic that broke off is connected to the graphics card on the motherboard and is nowhere near the RAM storage area.

I came across an application that regulates the Fan called SMC FanControl. app I put it on my iMac and hoped it might help the MacPro too should I ever get it operational again.

I've always found tons of stuff online relating to booting issues on a Mac. One thing you can try is to remove the most recent drive you installed. You didn't say, but the machine will default to another drive if it has another hard drive with an OS on it suitable for booting. You can also try starting up holding down the option key, and choices might appear if the board and ROM is good and it spots a boot alternative. I wouldn't worry about the tiny piece of plastic. As long as the card stays in place to maintain the electrical connections, you will be OK.