The Western Digital Scorpio 320GB 2.5" Internal SATA Hard Drive is completely compatable with all Sony PS3 models. By purchasing this hard drive along with a hard drive enclosure you can turn you're PS3 into a 320Gb machine while using the original hard drive in the PS3 as an external hard drive with the enclosure. Also the enclosure can be used to put the new hard drive in and back up your PS3 files to before you swap the drives.
1. Put the new 320gb hard drive in the new enclosure bought from play.com
2. Plug the enclose into the PS3 format the external drive then back up the utilities
3. Remove the new 320Gb hard drive from the enclosure
4. Remove the original PS3 hard drive and swap for the new 320Gb one
5. Insert the original PS3 hard drive into the enclosure then format it
Done now you will have a 320GB PS3 + External Hard Drive
Western Digital Scorpio WD3200BEVT 320GB 2.5" Internal SATA Hard - £44.99
This is the cheapest that i have found this hard drive on the internet, very reliable brand if not the best. From play.com.
Sweex STO30B3 2.5" SATA HDD USB 2.0 Enclosure - £6.99
This is the best enclose you can buy from the same retailer that has usb 2.0 for as cheap as possible.
This is a tutorial how to do all this!http://www.youtube.com/watch?v=AuyQPW3bDS0