I ask the question because i recently had to send my PS3 back to get repaired/replaced but I had put a 320GB Hard drive in it, in case it was replaced I didn't want to lose that HD but I'd lost my original 60GB HD so I bought I cheap replacement to put in the PS3 before sending back.
When my PS3 came back repaired I booted it and all 4 user accounts from my PS3 were on the system but I had assumed these would be on the HD i'd taken out.