I have this new problem with a Pentium III 533 Mhz Processor:

It was running fine for the past 2 years. Then recently, after putting in another 128 Mb memory stick (don't know if its related or not), the system will hang. A lot of the time, it will not post. When it posts again, the BIOS loads with a 'System hung for improper CPU speed setting', but its been at this setting for ever, and its not improper. The computer will freeze/hang at seemingly random times, the last time was half-way through a windows load, before at random points during use and it even hung while checking the settings in the BIOS. I should also mention that this computer has been very stable beforehand and rarely, if ever, froze before this started happening. Generally, when the computer hangs, it won't turn on again (POST), but the lights will light up and CPU fan will spin, however the monitor will register nothing. Occaisionally while booting up and not posting, the computer emitted a series of long beeps and long gaps.

It does recognize the new 128 Mb totalling 192 Mb, but was having a problem doing so at first. I checked the CPU temp in the BIOS, and it was around 45.5 degrees Celsius, which doesn't seem high at all.

Try resetting the BIOS to defaulst values, also if the default is for the drives to be autodetected then that will not be a symptom of a failing CMOS battery, but changing CPU can be...so also try changing the battery.