Originally Posted by Sterist
I just did this tonight actually. You have a few options.
You can backup your old HDD to an External Device. When the new drive goes in to your system (for a FAT PS3), it simply asks you to format this new drive if it is not FAT32. This new drive then gets formatted, and your PS3 works like normal.
Afterwards, you can restore your backup if you want. If you backed up a PS3 with Homebrew on it, including backed up games in a GAMEZ folder and cracked PSN games, these will also get backed up, including any retail content you purchased.
The only thing you lose, are your trophies, because they arent synced with the server unless you have PSN access and can do this.
For a SLIM PS3, you need a PS3UPDAT.PUP file on the root of the USB device you are restoring to I believe. Otherwise it does not let you restore, or format I believe.