Inspiron 6400 notebook

You have 2 slots that support a maximum of 2 GB total. 1 GB in each slot. The RAM for your system is PC2-5300. Hope this helps & please remember to rate my answer. Thanks.

Memory 
Memory module connector
two SODIMM connectors
Memory module capacities
256 MB, 512 MB, 1 GB, and 2 GB
Memory type
1.8-V SODIMM DDR-2
Minimum memory
256 MB
Maximum memory
2 GB

Here's how your add... http://support.dell.com/support/edocs/systems/ins6400/en/sm/memory.htm#wp999869

There are two slots for memory on that laptop and it will take a maximum of 2GB of RAM. The memory type is 1.8-V SODIMM DDR-2.
The cover ont he bottom if the laptop is easy to access and add more memory.