Well, after all the research on the net, I came up with a conclusion.
The Intel 810 chipset is said to support 100MHz FSB. I heard a guy
that used a 133MHz FSB capable processor and it worked fine, the only
thing is that the BIOS was showing some strange message.

According to the Intel's website, I can use the PIII processors with
the CPU Speed from 600MHz to 1GHz, but only with a Bus Speed of
100MHz and 0.18 micron and a Package Type of 370 pin.

I'll try that processor then. The reason is that I's like to use this
PC with Linux to make a firewall or printer server, and that's why I
am looking so hard about "old" stuff.

Thank you very much for your help.