Just out of curiousity, I wonder how the memory tests out with either the Compaq diagnostics (run from a floppy) or MemTest86 (boots/runs from a floppy -
http://www.memtest.org ) . . .
It might be a memory setting in the Bios setup rather than the module itself = the diagnostics might help figure that out for you. Compaqs generally prefer CAS2 single-sided modules [premium modules]. --- If the 128mb module was a recent addition, it might not be a great match for the notebook, and if it's under warranty, you could return it (or exchange it for a better matching module) if it doesn't pass diagnostics, or doesn't match the Compaq's requirements. Notebook memory is fairly pricey, especially the older PC100/PC133 modules - which are now in short supply. eBay auctions sometimes have used modules for less if you want to take the risk, and if the shipping doesn't eat up the price differential.
. . . Gary