Hoemee, The maximum size drives you can us on your current configuration is 300gb hard drives part number D5796. No in regards to the warranty; They can be extended to the 5 year mark from the date of purchase, then they become End of Life if we don't have part availability. If parts are available then a server can be made an exception and extend past the 5 year mark, unfortunately the 1800 doesn't fall under this. 
Hello, I have a couple of questions - first, I have a Dell PE1800 server that was replaced by a T710 for a customer.  I am using it on my bench as a test server.  The s/t number is  .  Right now it has 6, 73GB HHD's in a raid 5 config.  What is the maximum capacity HDD's I can put in this thing, replacing all six to freshen them up?   Also, before replacment, the customer replaced the motherboard, both power supplies and a HDD due to physical failure (during the migration - fun!).   My other question is - I know this server is out of warranty, but does Dell entertain the purchase of a new warranty contract and return to service of this server?  All purchased and installed parts have been drirectly from Dell.   Thank you  
Increasing HDD capacity and warranty stuff