You are on crack.it can only read PC133? I thought it was interchangeable. I know PC133 runs just fine in PC100 slots, it just throttles down. But PC133 slots should be perfectly compatible with PC100s. I know my mom's toshiba laptop takes PC2100, but i was using a PC2700 stick in the second slot. I tried the opposite, and the PC2100 worked just fine in a PC2700 slot. Maybe the stick is just totally dead...
-digital
PC100 will not run in a PC133 board. Ok, sure you can cram the stick in there. Heck if it was a god module with an SPD chip it could run ok. However most of the time the answer is no.
By running the PC100 stick, he drops the bus from 133MHz to 100MHz. This places a large bottleneck in the system, which of course affects overall system performance.
Remind never to hire you as a tech.