Please check the following recommendations to avoid overheating issues:
*Update the BIOS to the latest version in order to have the proper microcode of your processor, which will help on the proper recognition.
*Check the processor and system fan(s) to see if any have been disconnected or are blocked by a foreign object.
*Make sure that there is proper airflow in and around your system. Make sure your system is not located near walls or in corners. If vents in the system become blocked, airflow to the fans may be restricted.
*Your system should be kept in a room that has adequate cooling; the room's ambient temperature should be below 90 °F (32 °C).
*Check that the processor's heat sink has been installed properly. Inadequate thermal grease on the heat sink can cause unusually high processor temperatures.
*Make sure your system's I/O (disk, floppy, CD-ROM, etc.) cables aren't restricting airflow in the system.
*Please ensure that both the power supply and chassis comply with the ATX 2.03 standard (also called "ATX12V"). It is advised that the output be at least 450-Watts with 1 Ampere in the +5 Volt Standby channel.
*It is also recommended you try with a Thermally Advantaged Chassis. Please check the following website to identify a thermally advantaged chassis:
If further troubleshooting assistance is needed, feel free cntacting your local support group during business hours: Phone Support
Everything you've mentioned apart from the BIOS update has been done. I can't update the BIOS as the computer doesn't stay on long enough for it to update... sometimes it's not even on long enough to open the BIOS.