Davenrino,
Well, I sure know a lot more about bus clock speeds and multipliers than I did this morning!
I had a go at modifying the FSB (front side bus) speed on my BIOS. I changed it from 100MHz to 133MHz. But oh! When I tried to boot up, my system just died. The monitor went into standby mode and remained blank. According to the Asus A7V133 mobo manual, the system can become unstable, or hang, with some settings, but you're supposed to be able to restart the BIOS in safe mode. That didn't happen, so I had a dead PC that I could not start.
Luckily I had a copy of ADOBE and my mobo manual in .PDF format on a CD, so I took the CD to a friend's house and printed out the pages concerned with setting up the mobo in jumper mode or jumper free mode. I realise now that the multiplier is set at 12, and this is correct. The other value, 100MHz is multiplied by the first value to give a result of 1200 - and that's as it should be for my Athlon 1.2GHz, given that I do not want to overclock it. I had to open up the case and move one jumper to set jumper mode, then set one bank of DIP switches to give a multiplier of 12, and the other bank of switches to specify 100MHz bus clock speed. After that, the system booted up again just fine.
I think I'll leave those settings alone from now on!