Thank you for the replies and suggestions - I've managed to fix my system now, or at least find a workaround. I had a look at the different hardware driers I installed but it was Oleg_II's suggestion that uncovered the source of the problem. It seems taht the latest Win2k update rollup (KB891861) both V1 and V2 may have a bug in the new "hal.dll" it installs for AMD X2 dual-core processors and perhaps also P4 hyperthreading or other SMP CPU setups. The original filename for this Hardware Abstraction Layer version is "halmacpi.dll" which is the ACPI Multiprocessor PC HAL. The Win2k SP4 version is 5.00.2195.6691 and KB891861 updates this to 5.00.2195.7006 - which exhibits the temperature bug with SMP systems. I looked up the \WinNT\System32\$NtUpdateRollupPackUninstall$\ folder and found the backup SP4 version and then replaced the updated "hal.dll" file with this backup version and now the temps are fine and in line with the WinXP installation on my dual-boot system (33c idle). This temperature problem was driving me crazy with puzzlement so many thanks to you all for your input and especially to Oleg_II!