What happens when you try to play a backup game in a psx without modchip or bootcd?

[spooky]

With no mod chip installed i would expect the "insert PSX disc" screen or the memory card screen.

When you said "the playstation screen comes up" was this the screen with the PSX logo on a black background? If so then the PSX recognises the disc but is failing to continue booting for some other reason (mod chip is installed). If your talking about the first PSX logo you get when you turn the PSX on (orange/red logo on a white background), then its probably not moded.