The problems listed below are not directly related to overheating, but you should check them as well.

• Loose motherboard: Your motherboard must be very well fastened to case's metallic frame. We've seen many cases where the computer gives random resets or crashes when the desk was rocked, just because the motherboard was practically loose inside the case. In other cases, it is very common for the PC to lose its machine setup when a new daughter board is installed, as motherboard bends (due to lack of padding points) and some of the motherboard soldering points contact the metallic frame. Therefore your motherboard must be very well fastened to case's frame, using the largest quantity of fastening points as possible. To learn how your motherboard should be correctly installed to your case, read our tutorial How To Install a Motherboard.
• Hard disk flat cable: If you still use a parallel IDE hard disk drive (e.g. ATA-100, ATA-133) instead of Serial ATA (SATA), you should check carefully how it is installed. Parallel IDE hard disk drives use a 40- or 80-wire flat cable that normally has three connectors, one in each cable end and one midway. The hard disk must be connected to one end of the cable and motherboard to the other end. The midway connector stays normally loose. It happens that some technicians connect the hard disk to the midway connector, is such a way that a cable end connector hangs loose (see Figure 6). This is not good, as this stretch of the cable will actuate as an antenna, receiving and injecting noise in the data transmission, and as such hard disk transfer rate will be reduced. Also, if your hard disk cable is using a 40-wire flat cable, we recommend you to replace it with an 80-wire cable.

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Figure 6: Wrong IDE hard disk drive installation, using the midway connector. Don't do this!

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Figure 7: Correct IDE hard disk drive installation, using both ends of the cable.

• Optical drive as hard disk slave: Also if you still use a parallel IDE hard disk drive, the optical drive (CD, DVD, etc) must be installed in the secondary IDE port of motherboard, configured as "master". Many people install the optical drive on the same cable as hard disk (using that midway connector that stays usually empty), as "slave". In that way the hard disk drive and the optical drive will have to strive for cable utilization, as they use same cable, and both devices can't change information with the system processor simultaneously, reducing computer performance. If your computer optical drive is sharing the same cable as the hard disk drive, undo this installation: install it on the motherboard secondary IDE port as “master” (you will need a 40- or 80-wire flat cable). Newer motherboards, however, are coming with just one parallel IDE port (see Figure 11), giving us no other option than installing the optical drive and the hard disk drive on the same cable. If this is your case, we highly recommend you to replace your hard disk drive with a Serial ATA one in order to leave the optical unit alone on the parallel IDE port, thus increasing system disk performance.

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Figure 8: Hard disk drive and optical unit are sharing the same cable. Don’t do this if your motherboard has two or more parallel IDE ports.

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Figure 9: Parallel IDE ports on a motherboard.

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Figure 10: Correct cable installation.

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Figure 11: This motherboard has only one parallel IDE port, so the “wrong” installation is our only choice. In this case we recommend replacing your parallel IDE hard disk with a Serial ATA one.