.cab files are cabinet files that are compressed to conserve disk space for distributing programs (ie. games) so it could be for any program and must be the specific cab file you are looking for for that installer - without knowing what you are trying to install we can not know where you might find it (but it should be a part of the disks or download files for the program you are trying to install and thus should be on one of the disks included with the program) -- also does the error say specifically that it is missing or does it say it is missing or corrupt ? could be the install disk is scratched or otherwise corrupted so that the install program can not read it properly even though it is there on the disk in which case you would...
.cab files are cabinet files that are compressed to conserve disk space for distributing programs (ie. games) so it could be for any program and must be the specific cab file you are looking for for that installer - without knowing what you are trying to install we can not know where you might find it (but it should be a part of the disks or download files for the program you are trying to install and thus should be on one of the disks included with the program) -- also does the error say specifically that it is missing or does it say it is missing or corrupt ? could be the install disk is scratched or otherwise corrupted so that the install program can not read it properly even though it is there on the disk in which case you would need a new copy of the disk\download files.