Yes you can replace your HDD and no it doesnt void the warranty.
First thing to to is back up your data to an external HDD as Im sure you will want to keep a lot of your game saves. I used a USB HDD for this and it worked with no issues - the PS3 backup utility does this for you.
Next on the left hand side of the console is a small flap that can be removed with a flat bladed screw driver.
Unnder the flap you will find the caddy is secured with a "blue" headed screw, undo this and the caddy will slide towards the front of the console.
With the caddy removed undo the four screws securing the drive - this will then release the HDD.
Replace the HDD with your new / larger capacity drive.
Replace the four screws and slide the caddy back in, then replace the blue screw.
Power up the PS3 and you will get a message saying the new drive needs to be formatted before use. The PS3 will take care of the rest, leaving you just to copy your backup data onto your new drive.
Firmaware and users settings are stored on ROM.... job done
Hey Thanks guys your are great. That will help tremendously. Have a lot of data right now and it's getting really close w/ all the games and other such stuff. 2.5 and sata w/ 5400 RPM got it. Damn i wish it wldn't cause a heat issue w/ 7200. May buy a cooler and go for that.
I was having the same problem but when i tried to change the hard drive this message appeared:
The system software cannot be run correctly. Pless the PS button to try to restart the system. If the system can not be restarted the system patition of the system storage must be reformated and you must reinstall the system software. connect storage media that contains update data of version 4.20 or later. Then press START and SELECT buttons at the same time. I have tried to restart the system and get the smae message, I have tried to use an external harddrive that I backed the data up on and I get this message, No applicable update data was found. Connect storage media that contains update data of version 4.20 or later and then press the START and SELECT buttons at the same time.