It will not affect your warranty.  RAM purchased from Dell carries a limited lifetime warranty, and adding more from approved sources does not affect the status of the existing system warranty.

Instructions for installing RAM can be found in your current system documentation under "Adding and replacing parts" - "Adding Memory."

ok thanks! and also do you know if kingston ram is approved and will keep my warranty intact?  will my pent 4 1.6 processor be able to work well with an additional 512 mb ram or do you think this is too much? thanks so much.

I know that some Kingston RAM has been known to be a big PITA on some Dell systems, and I wouldn't use it.  Dell or Crucial would be your wisest bets.

http://www.crucial.com

I have had good luck with crucial or micron from ebay.  Buy from a reputable seller with great feedback.  First go to crucial to find out what exactly it is you need, then search for memory on ebay reflecting those specs.  This is where I have had good luck.

Also, adding 512 more is not too much.  512 is the minimum I would run if you want your computer running speedy and effecient, so either a stick of 256 or 512 will do.

Go with 768 if you plan to keep your c840 another couple years.  Or, if you plan to upgrade soon, stick with adding a stick of 256.  If you look at the newer latitudes, see if they run the same memory type.  if so, you could always take your new stick and add it to you upgraded computer down the road.  I know the d800 still runs the 266mhz.

BTW - is there a big difference between ruinning the d800 w/ 512 266mhz  versus it with 512 333mhz ram?  ( i know you have to do a "work around" to get the d800 to run with 333mhz.)

 

As far as I know you can't have "too much" ram. Can someone cofirm this? I always thought they had very little correlation...you could have a 1 ghz processor and 3 gb of the best ram...now that wouldnt be smart because the processor would be your bottle neck for computing power but, it wouldnt actually cause any problems would it?

More RAM can make systems run hotter, which is sometimes a problem for notebooks.  Also, Win9x (98SE, ME) operating systems don't recognize more than 512 MB of RAM without some adjusting.

I am quite sure that all systems have a cap for how much RAM they will accept.   But newer systems can hold quite a bit.