Do u find solution guys?

The .mcr file should work. PBP is the format for the image of the PS1 game, not the save game. After launching the emulator you will have pull up the retroarch menu to point the memory card location to wherever your .mcr or .gme files are and it should work. I think it also helps if you are using a BIOS file for the PS1. I know it works but it's not the easiest thing to do.

Problem solved!
Turns out I was missing the PSX bios. Don't know how I managed to play other games without ever needing them, but once I paid attention to the message "bios missing, add them for better compatibility" and placed them on the BIOS folder, everything turned out better. Games that crashed before no longer do so and I can now switch discs on Resident Evil 2 just like you all told me (eject, switch, close, reset) from the .pbp file.

@treedude well that sucks. It would be nice to be able to rule that out. But the xbox driver might be an issue too...

Thank you,

that sounds much easier than what we did. I'll have to try that one out :)