1.Pull out your hard drive from your PS3
2.Connect the hard drive to your PC
3.Do a FULL format, not a quick one (a quick format just formats the boot section and root directory of the hard drive, and not the data on the hard drive. We want the hard drive blanked out). Make sure to do it in FAT32 (if you can). To format the HDD you'll need to go to Control Panel --> Administrative Tools --> Computer Management. This has an older windows feel to it, but on the left hand side you'll see Storage, under that (you may have to click and expand it) you'll see Disk Management. Click on that, in the middle window will come up the hard drives. You should see it there (It'll likely have a series of letters, followed by numbers). You may not be able to format it into FAT32 format with it being such a large disk drive (windows doesn't like giving you any non-MS file format for large disks). But doing a NTFS format should work. There are a few programs that will allow you to format it into FAT32 if you can't with that program.
4.Put the hard drive back in the PS3 (be ready with a USB thumbdrive with the system software on it, follow this link to learn how to set it up).
5.Hopefully, your PS3 will boot up, and prompt you to install the software on to the hard drive
6.Time to download all your stuff again (hoepfully you haven't purchased any movies, as you can't redownload them). Then, back to gaming