There seems to be a lot of confusion surrounding the various file formats that
Jaguar programs come in, and a lot of this confusion seem to come from
Cowering's GoodJag renaming tool. Note that it simply gets some files wrong,
and it also incorrectly renames cartridge images with an extension that
belongs to an already established extension (.jag is a Jaguar Server
executable--read on). To clarify, there are basically four major types of
Jaguar binary images that are NOT cartridge images:
.abs
.jag
.rom
.bin
The first type, the .abs file, is a DRI/Alcyon format absolute location
executable. These come in two different flavors and contain load and run
addresses in their headers. Note that some files which have an .abs extension
are really incorrectly labelled .bin files with no header information
whatsoever.
The second type, the .jag file, is a Jaguar Server executable. These files
contain header information that tells you where to load and run the file's
executable code. Note that as of this writing (1/1/2004) that the GoodJag ROM
renaming tool by Cowering incorrectly renames Jaguar cartridge ROM dumps to
have a .jag extension (a better choice, and the one supported by Virtual
Jaguar, is .j64)--if you're trying to run a ROM image with a .jag extension on
VJ, it will misinterpret it as a Jaguar Server executable and likely fail to
run.
The third type, the .rom file, is an Alpine Board/ROM Image file. These files
have no header, but are known to load and run at $802000 in the Jaguar memory
space. Again, these are *different* from cartridge dumps since they load at a
higher address than a Jaguar cartridge.
The fourth type, the .bin file, is simply a Jaguar executable with no header.
Since these files contain no information about where they load and execute,
Virtual Jaguar does not support this file type. Go bug the author to release
either a file with headers or a file in Alpine ROM format. Virtual Jaguar is
not omniscient!

There is a fifth type of file that is supported by Virtual Jaguar, the .j64
file, which is simply a 1, 2, or 4 Meg dump of a Jaguar cartridge ROM which
loads at $800000 in the Jaguar memory space.
Basically, if it's .COF, .JAG or .BIN, it's very likely a homebrew, not a ROM dump.