If you can’t run unsigned code, you cannot install emulators or converted games. Install or PRO-C to unlock your PSP’s potential.
Most "Resident Evil 4 PSP" files found online are not official games but rather: Resident Evil 4 Psp Iso Highly Compressed High Quality
While many sites claim to offer a " Resident Evil 4 PSP ISO Highly Compressed" file, it is important to note that there is no official Resident Evil 4 release for the PlayStation Portable (PSP) If you can’t run unsigned code, you cannot