Hi. I'm new to this scene and I noticed that some downloads for PS1 games are in parts. When I do download these files, can the PSX use them as is or do I have to convert them. Much thanks in advance.
you will have to unrar them using winrar. also, check the file format and depending on the emulator, it will run it as is. sometimes people like to use weird file formats like .bin/cue, mds/mdf, .nrg, .cdi, etc. the .iso is just fine for PSX games. .cdi is more common for dreamcast games anyway. if it doesn't run as is, then use mounting software like Daemon Tools to mount the image and play it like that through a virtual drive.
Some ISO formats work better than others. Or mount the image, use a program such as ImgBurn to create a image from that virtual drive image or mounted image. Just make sure all the parts are in the same folder, and extract one. It should do it correctly.