Where did all that memory go!?

I have an original 60gb PS3 and regularly delete game data etc from it to ensure I always have plenty of space for new stuff. I always keep my game saves, but installed game data is first to go as it can be several gb's per file.

So I've deleted everything that I need to, leaving me with just 25gb available space. I don't have ANY photos or videos on the PS3 at all, I've always kept those on a separate external drive. I've added up what game data I have left on there, and it only comes to about 9-10gb(?) Now, I wouldn't expect that I have precisely 60gb of space, since often you lose some of it with the OS and other features, so was expecting something maybe about 55gb in total.... but 25gb + the 9gb of stuff I have installed is absolutely nowhere near this figure, which begs the question; where the hell did all that memory go?

I'm reasonably tech-savvy so I know 100% that I've checked everywhere that the PS3 menus allow, and I have nothing else whatsoever apart from game saves which add up to virtually nothing, and the 9gb of game data. A friend suggested that everytime I've downloaded system updates and the like, that these are not deleted - but there isn't anywhere I can access that shows me these files if I do still hold them, so I can't delete them even if I wanted to. Furthermore, I highly doubt that the system updates I have downloaded add up to anywhere near the "missing" 19-20gb that I can't account for anywhere....

So what to do? Do I format the thing and if so - can I extract all my important stuff like trophies, saves etc? Can anyone suggest where all this space may have magically disappeared to?

take into account game data that is installed from a lot of games now and that is usually 4-5GB when a game has that initial install. Then take all your game saves, and the about 6-7GB you alread lose with the OS etc. Also if you have multiple USER ID's dont forget to add up all the saves there as well. Have you ever deleted your messages from friends sent/recieved its not a lot but if you have never done it before it can add up. on a 60GB hard drive you start out with about 54GB-9gb of saves that leaves you with 45GB so you are missing something 20GB worth you are not paying attention too

I'm pretty sure some DLC doesn't show up in the Game Data section so I'm not sure where you can see it!!

Thanks for the suggestions so far guys - sadly, none of them still add up though. I don't have any DLC, so that's out... I just don't have anything else installed or saved anywhere that can account for a 19-20gb missing amount(?)

I think I will just find a way of getting my game saves off it and just format the thing.... the mystery of the missing storage is driving me mad though(!!)

Did you take into account any downloadable games you may have as well. Its something you are just not seeing i promise you, or your not adding it up correctly. Do you have a lot of themes downloaded etc.