Locate changed files

[SCW]

OK... I have a question that is outside my area of expertise:
Lets assume someone ;-) began using PS V 1.3 added the PrestaBook theme, but also made some changes to the
core tpl files - without making a note of where - duhhh and not following the templating guidelines.
Now... is there a method by which the modifications can be located/identified and then structured correctly so they will not
be overwritten in a migration to 1.4?
In other words, is there a way to "compare" the original installation of PS to the current modified version to locate where changes have taken place?

Thanks!

[tomerg3]

I use a program called Beyond Compare, it lets you compare folders (and see which files are different) and compare files (and see which lines are different)

[SCW]

This could be exactly what I need - thank you!