I had 3 x 128mb PC133 SDRAM.
I bought 3 x 256mb PC133 SDRAM to replace them.

The PC won't even boot up with them. I've tried one of the new with two
of the old etc. - every combination I can think of, but in vain. I've
had to go back to the 128s to be able to type this, obviously.

Someone told me there is an mb limit on each slot, depending on the make
of motherboard. I presumed that must be the cause, however I've just
downloaded a helpful little program called "SIW" (systems info Windows)
and it says:-