Memory Question

I have recently tried to upgrade the memory on a relative's older
Dell, but encountered a problem that I haven't had before with my
homebuilt systems.

It is an Intel board that had 2 DIMM slots and was spec'd to handle
512MB of RAM (it was hard to tell which chipset Dell used). The CPU
is a celeron 566. As you can't exactly buy PC66 anymore, I got a
256MB PNY stick of PC133 (it was an 8-chip module). The packaging
said the memory was for PC's running 1Gig or faster. The PC gave 3
short beeps and wouldn't POST. I upgraded the BIOS to the most recent
version Dell had for that model, but that still didn't solve the issue
only now it wouldn't even beep at me. The PC worked fine after
replacing the module with the stock 128MB stick.

That leaves me with questions:
1) Could this problem be due to the memory density (32meg chips on the
module)?

2) What does the memory care what the multiplier is for the PC? Why
spec the module to be for 1Gig PCs?

-Greg