This rather simple guide for patching savegames for PS1 emulated games on the PSP, assumes one or two things
1) You have a hex editor (if not grab one, eg, hexworkshop)
2) You have a custom built eboot.pbp ready to go
3) You have ultraiso (or any iso management tool for your os)
4 optional) You have PSPBrew 0.90 (for changing icons)
If you have the above you can move on.
Obtaining the GameID
First things first, we need the GameID from the game you have just rebuilt into the eboot.pbp, for the sake of giving an example i will be using Final Fantasy 7 (US).
Open your game image using ultraiso, and you will see numerous folders, and somewhere near the bottom a file named SCUS_941.63
A file starting in S*** is always located in the root of playstation disks as it is the boot file.
Once you have the name of the file copy the filename to notepad, here you can delete the _ and . from the filename, you should now have SCUS94163
Embedding the new GameID
Now we have the GameID, open HexWorkshop.
Note : unless you have alot of hdd space and ram, editing 500+mb eboot files will sometimes fail, to remedy this, go to Options > Preferences, then in the options menu under Configuration tab, check the box named "Enable direct file writing" and restart hex workshop, be warned though, this writes directly to the disk so any changes you make a permanent so make sure you do it right!)
Now open your eboot.pbp with hex workshop
You will see straight up at 00000130 the line SCUS94476....... change this to SCUS94163....... (to reflect the new GameID code)
Now, scroll down, or use Goto (ctrl+g) the Hex value 50400 or 00050400 if you want to just scroll there.
On this line you will see _SCUS_94476..... notice that this one has _ around the S*** code, these must remain intact, so edit your code to fit in this gap.
An example for a completely diff game :
For this tutorial we shall change this to _SCUS_94163.....
Fixing the GameName and Savedata names
Back up at the top you will find on line 00000350, either "Hot shots golf 2" or "Playstation", Change this to whatever you want it to be
for the sake of the tutorial i changed mine as follows :
4646372043443100000000 FF7 CD1
This will show up if you triangle > show info, on the games eboot icon :)
Further down, (at 0005122C) you will find Hot Shots Golf..2, with the hex 486F742053686F747320476F6 C66C2AE32, you can edit this line (as long as you start at the H) to anything you want, as long as you clean out the first with 00's if it's not as long, for example :
486F742053686F747320476F6 C66C2AE32 Hot Shots Golf..2
46696E616C2046616E7461737 920370000 Final Fantasy 7
You can even go longer than the original, like this :
46696E616C2046616E7461737 92037205361766564617461 Final Fantasy 7 Savedata
This will give them the right name under the savegame manager, too :)
OPTIONAL : Changing EBOOT.PBP Icons
Place your custom files in the same directory as popstation.exe with the filenames PIC1.PNG, PIC0.PNG and ICON0.PNG, popstation will then use your icons when creating the new EBOOT.PBP of your game.
To edit AFTER making the eboot and changing your Savegame ID, simply open the eboot.pbp in pspbrew (tkaes some time for huge eboots), and select new icons for :
UNKNOWN.PNG (PIC0.PNG, the overlay, not really needed)
Then his save, and use this eboot.pbp in your game folder
Hint : Get some custom made ones here :
Its worth noting that the eboot can be run from ANY folder in /psp/game/ so just name them how you want.
For example, /psp/game/final fantasy 7/
All savegame data will now be saved in /psp/savegame/scus[COLOR=Purple]94163/ instead of the hotshots golf 2 dir.
Do this for all the games you make and you will be able to continue each game without starting over as the savegames wont overwrite anymore.
For multi disk games (like final fantasy 7), use the same S*** code as disk 1 (even if the other disks use different codes), that way when you come to switch eboots, it will load the savedata from earlier play and allow you to continue without any problems.
!! IMPORTANT NOTES FOR DOING THIS !!
1) If you do this AFTER playing the game you've modified, chances are you'll get an error, this is caused by the savegame from the previous boot, because it has a new ID it will no longer work properly, you must restart savegames from scratch for them to work (just delete the old folder and start the game again).
2) If you have used PSPBrew on the eboot BEFORE doing this, chances are the location of the savedata ID will be different, for the sake of making life easier, use pspbrew AFTER modying the savedata id.