What is the "READER" Partition?

Are you sure it's the hard drive, and not a flash card reader?

It is used in conjunction with the Latitude ON module.

Thank you for your response.  Could you please tell me what a "Latitude ON module"  is ?  and why does it need a dedicated drive partition?

If I have to keep it, could I re-assign the letter to something low on the list like "X"?

It is an instant-on option that allows you to do some work without waiting for Windows to load.  It needs writeable space to function (it operates from flash ROM in the computer).  If you don't have an ON module, you can do what you wish.  If you do, leave the partition intact.

Thank you for your response,  I was hoping to remove some of the clutter from the computer.

I have not been able to find any program or file called "ON Module".  The computer has Windows XP SP3, and as far as I can tell, it is a typical Windows XP setup - it does nothing until Windows finishes loading - then you can start the other programs.

How can I tell if this module is loaded?

It's not software - the ON module is a piece of hardware:

http://www.engadget.com/2009/12/19/dell-adds-cheaper-latitude-on-flash-module-to-some-laptops/