Hi all. Well it seems I've learned another lesson the hard way. I ordered a 256mb SODIMM PC100 32x64 for my Thinkpad 600x 2465. WRONG! I had no idea that notebook memory was so picky., as this is the first laptop I've ever owned, so I did not bother to do my homework before ordering. In hindsight, I should have checked the existing memory stick for the make and ID numbers associated with each chip on the SODIMM to see waht speed it actually is. It already had a 64mb Kingston KTM-TP390X/64 8m x 16. Needless to say when I put the 32x64 SODIMM in there, it wouldn't even POST. I have a couple of questions on this. What does the "32 x 64" mean. Why are these SODIMMS so particular. I mean there seems to be an endless variety of 144 pin modules out there. It also seems the older the SODIMM, the more rare it is, and thus, more expensive! A 8m x 16 stick seems sort of rare, as not many sites like Newegg and tigerdirect carry that type anymore. Crucial and Kingston carry it, but I would like to know if there is another way to find out about compatibility besides filling in the "memory chooser" drop down menus. I'd like to shop around for a stick. I made the mistake of ordering before I knew the whole story, and now I have to return it, and I'm not sure if they have a compatible type in their stock(computergeeks dot com). I'll probably end up having to give them a re-stocking fee and only get part of my money back. I hope someone else can learn from my experience before they buy!