Hello and welcome to Bleepingcomputer.
I believe you have a laptop computer and if this is correct this should be your support page from Dell. http://support.dell.com/support/DPP/Index....stemID=XPS_M140
Here is the download section for your manuals in case you need them.http://support.dell.com/support/edocs/syst...0M/en/index.htm
This is the information I found on what type of memory your laptop supports.
Memory module connector two SODIMM connectors
Memory module capacities 256 MB, 512 MB, and 1 GB
Memory type 1.8-V SODIMM DDR-2
Minimum memory 256 MB
Maximum memory 2 GB
This is the type of memory your laptop supports.
Here is a pdf version of your owners manual. http://support.dell.com/support/edocs/syst...en/om/om_en.pdf
Exactly what type of memory are you trying to add to the laptop? If there is any numbers on a sticker on the RAM please post those numbers.
Thanks in advance.