I have come across fichero and archivo although the latter seems more ubiquitous. Is there any difference in usage? Or is it just a matter of personal preference? Also, if archivo is file, what's the Spanish for the actual archive folder as found in many email accounts?
Fichero is more common in Europe (Spain) while Archivo is common in Latin America.
I would suggest you use Archivo, based on these definitions:
Archivo: A group of well-organized documents managed by a person or enterprise.
Fichero: Is a furniture to keep organized documents.
But in IT, both have the same meaning which is a collection of information stored somewhere (devices, memory, etc).
I think Spaniards use fichero because in the past they stored their documents in cabinets but for Latin Americans it was not limited to cabinets. It's is also related to the way you organize your documents in a cabinet, binder or folder.
In case of archive folder in emails it's a little bit different because for Latin America it is used as an adjective Archivado (singular) o Archivados (plural). This means to keep your files, documents or emails away from your current ones for a later search. The same intention as in English.
As with many computing terms, fichero and archivo competed against each other for dominance, and at this point it's pretty clear that archivo will be the victor.
In computing contexts, you should use archivo for file.
For archives in the long term, out-of-the-way sense, archivo (with its verb archivar) are also used. There's not much confusion generated by the overlap of terms especially when you can use the verb form.
For other files (like police/academic/medical), in my experience, the most common term is expediente. As aprendedor notes, you can also hear dossier (with double S per the DRAE), though that can also be used for a report.
I work in the IT world and some people use "archivo" and some use "fichero". We understand both terms are used for files
The folder to archive mails is called "archivo", and the real life term used in Spain is "archivo" as well, "fichero" is almost never used besides computer related stuff. As Maximus Decimus says, "fichero" is a furniture, while "archivo" is a concept. I can't really talk about the other spanish speaking countries