Just test by yourself 
Put the save from Disgaea 1 in \memstick\PSP\SAVEDATA and you will see if you can do this
Edit : @TheDax >> You're too fast

Put the save from Disgaea 1 in \memstick\PSP\SAVEDATA and you will see if you can do this

Edit : @TheDax >> You're too fast
♦ Intel Core i7-6700HQ | 16 GB RAM | NVIDIA GeForce GTX 960M | Debian Testing
♦ Intel Core i7-2630QM | 4 GB RAM | NVIDIA GeForce GT 540M | Debian Testing
♦ PSP-3004 | 6.60 PRO-C2
♦ Intel Core i7-2630QM | 4 GB RAM | NVIDIA GeForce GT 540M | Debian Testing
♦ PSP-3004 | 6.60 PRO-C2


