My computer is a Pentium II 233 MHz with 256 MB RAM and 20 GB hard drive running Windows ME. Recently when my computer boots the CPU speed is displayed as 133MHZ and on one occasion was displayed as 166MHZ. It runs very slow at these times, however, if I reboot, it occasionally corrects itself. If the CPU needs replacing can a 350 MHz CPU be fitted without causing any other problems, or should I stay with a 233 MHz?

As the computer operates ok, even when the CPU is operating at the lower speed, it is likely the CPU is fine, but the issue lies with the motherboard. From what you have said, the problem mainly occurs when you cold-boot the computer and it is occasionally corrected when warm-booting the machine. There are settings within the motherboard setup (called the BIOS setup) which allows the CPU clock speed to be changed to either run at a faster speed (overclocking) or slower speed (underclocking). It is possible that these settings are changing when you are booting the computer. Other people may suggest that you should flash your BIOS with the newest software from the manufacturer. However, I recommend against this for two reasons: the problem has only occurred in recent times (and the computer worked previously without an upgraded BIOS), and if you incorrectly flash the BIOS you will ruin your motherboard. My best guess as to the cause of this problem is the battery on the motherboard (which is used to retain the motherboard settings when the computer is off) has, or is slowly going, flat. So, each time your computer is turned off the motherboard settings are lost. Another way to confirm this theory is to see whether the computer clock is running slow or is displaying the incorrect time. In any case, you are well advised to take the computer to a technician to have it looked at, as there is little more I can advise you to do via correspondence.

Regarding your second question about fitting a new CPU, this depends on the motherboard’s chipset. The chipset dictates the physical processor socket format on the motherboard and other critical factors. If you wish to update the CPU in the computer, and keep the existing motherboard, you will have to ensure the motherboard chipset is compatible with the new processor. Even if you do determine the type of processor compatible with your motherboard, you are going to have trouble finding that processor as they are very old and you would not be able to buy them new. In fact, it is more trouble than it is worth. To upgrade you are probably best going for a whole new motherboard and processor (but you would probably have to get new RAM as well, which is compatible with the new motherboard). Have a look at the February 2004 issue of PC User which has an excellent guide on upgrading and a full explanation of different CPU formats, RAM types, etc’¦