iso's won't play on psx

[vagabond]

hi there,

this is gonna be kinda long, but here goes. i have recently acquired a few .iso files that i want to burn to play on my psx (which is modded). i have no problem making my own backups normally. however when i burn these new images, the 2nd screen where the PS logo normally is appears, but it says either "sony" or "main menu" at the top, playstation in the middle, and something else at the bottom. i've tried burning both the .iso files, as well as converting them to .bin/.cue files with little success. i have made good copies w/ dragon ball gt and batman forever, but no such luck with tenchu or samurai showdown 4 (which i really want) so if anyone has any ideas or has had personal experience with these files, please tell me what to do. i appreciate any and all help.