Sorry, my last comment was in response to apache_lives' comment. I found out it took EDO RAM by googling the model number, 2545XCDT. You'll come up with many sites, some of which are links to memory upgrades for this specific laptop from various companies. SO DIMM is small RAM; it's what laptops use. The laptop you have needs a SO DIMM of EDO RAM. You tried to put a SO DIMM of SDRAM in it and that's why it didn't work. Same size and form, but different pin layout. This website, http://www.ahinc.com/hhmemory.htm,
gives good descriptions/comparisons between the types and techs of RAM if you're interested.
I've looked briefly, but newegg doesn't sell EDO at all and amazon doesn't have 128MB modules of EDO SO DIMM. Might be much cheaper to ask some friends if they have any old laptops still laying around with EDO RAM still in it lol.