Download the update you want on your PC, assuming you're on OFW create a folder in the root of your USB, rename it to PS3 and another on inside it, rename it to UPDATE so it would look like this: PS3/UPDATE/put the update you downloaded here.. the update file will be like this PS3UPDAT.PUP
plug the USB to your PS3, update via storage media, the update will install and complete.. if it doesn't work try this: Reinstall the update again
1. Wait until installing occurs and pull out old HDD at 0%
2. Error should occur(let it run the count down and let ps3 restart itself)
3. You should be seeing a "press ps3 button on controller screen". On that screen put your new HDD in the ps3 AND have USB with update on it in the ps3.
4. Let it look for the update on the usb and download it / let the ps3 restart itself
5. Now you should be seeing the "press ps3 button on controller screen" again (don't worry)
6. Let the ps3 reformat your new HDD and let ps3 restart itself
7. After the reformatting it should reinstall the update using your USB again
8. If it worked you should see a screen with a PS3 to the PS3.
i hope this helps bro. PEACE