Memory Lapse

I'm looking for clarification on memory terms and the practical
implications.  Over the winter I built two new PC's and assembled another
one out of old parts.  At the time I kind of had things figured out such as
DDR, PC133, PC3200, PC2700, etc.  Now a friend of mine wants to add memory
to a couple of his PC's and I can't recall a lot of what I once knew.

One of the issues that I ran into was that the "notch" in the stick didn't
line up with the notch in the motherboard.  In my case I think that I had
bought PC133 and it didn't fit in my new motherboard so I just stuck it in
the old motherboard where it worked fine and did some reading.  I ended up
buying some PC3200 memory for the new motherboard and life was good.

Can anyone offer some clarity to the cesspool of terminology?  Thanks.

Dave Parnin
Nishikawa Standard Company
Topeka, IN  46571
daparnin@xxxxxxxxxxxxxxxxxx