it depends on what exactly was lost, but if the editor was active when the computer was crashed, then only part of the data can be restored - it is the reason why every computer technician ever suggests backups of important works.
the first step of recovering is that you must not store or copy any other file on the computer before the restore attempt.
if you do not do anything, then there are programs on the internet that can try to restore files where only the data association was lost and the computer marked the storage as "empty" without overwriting the old data.
the problem is if you work on the computer before doing the restore - if you do, the now marked "empty" HDD sectors will be overwritten by newer files and the old data truly erased.
No matter whether those programs work or not, what can almost always be restored from a project is most of the mapfiles. Only the current map, the map that was active when the computer crashed, is usually lost.
AFTER all other attempts to restore what files might be restored with the programs above, you need to go to your project folder and count the number of mapfiles there.
then make a new project.
in the new project, make new maps until you are one or two maps above the number of your old project. keep the maps empty grass, it doesn't matter what they contain, only the files matter.
close the editor
after that, copy the mapfiles BUT NOT the mapinfo file into the new project.
It is important that the mapinfo comes from the new project, not the mapinfo that was damaged in the old project.
if you did all things correctly, you'll find most of your old maps in your new project.
you'll have to check all events however because those events will have lost database connections - for example a treasure chest might contain the wrong item and so on.
