> I have v119 roms and would like to update them to v124.

Fine. Easy with cmpro. Load a 124 datfile (or even better, use the MAME .124 binary for a direct import) and run a full scan of your old .119 sets. After that, add new sets with either the rebuilder (prefered) or the fix missing option.

> However, I don't understand where/how to get the 'fix' files in order to do this
> update.

I don't know what you mean with 'fix' files but I assume you simply mean newly added/replaced sets since .119. As I said, let the scanner check/fix everything for you and add the new ones with the rebuilder. More details are listed in the (little outdated) documentation or follow tutorials.


> Are the fix files just about updates to the various BIOS files or also
> individual updates for various ROMs?

I still don't know what you mean with fix files. I assume these are simply a collection of new sets, maybe limited to only the changed files.



> When updating from one version to another I assume that it is just the ROMs that
> change and not the CHD files?

You're wrong. Everything can change. Roms, samples and chds.


Roman Scherzer