Dell Latitude C400 memory problems

i'm using a quite old dell latitude c400, and i would like to upgrade memory (adding an extra 512mb)

i cant afford buying from places like crucial - so ebay seems to be the only option.

 

my question is: does the latitude c400 use low or high density RAM, and what tells me if it is low or high (something along the lines of 64x64 or 32x8 or something similaraly confusing)

 

finally, what would happen if i put the wrong density in?

 

please answer as soon as possible

 

much appreciated

 

Benji