After doing a considerable amount of research although it now seems not enough I have installed an Intel Skt 775 3.6Ghz P 4 HT cpu in place of the 2.8 Ghz Celeron with a view to gaining the benefits of the extra processor speed and the L2 cache.
I find there has been no gain, in fact it seems the opposite has occurred and the PC seems slower in every respect.
I have checked the cpu speed using CPU ID and the Intel CPU identifier which correctly identify it but show the processor speed in the region of only 1860Mhz and the FSB at 533 not 800Mhz as expected. Also in device manager, depending on whether I set the hyperthreading to on or off I see two processors or one. I cannot see any way in the BIOS (Version 5 R1.11.240.02 9.12.2005) to change any other settings to counteract the problem. My questions relate to information I read about MICROCODE update and a possible BIOS update to accomodate the new CPU. Are either of these necessary and will they solve the problem? Help please on this?