If you have been editing and a crash occurred before you could save your files, then simply run Source Insight again. Source Insight will know that there were outstanding changes to your files because it will find orphaned recovery files. A dialog box will come up and indicate that a previous session with Source Insight did not end normally. At that point, you have three options.
Click the Recover button. Source Insight will proceed to recover all files previously opened. After recovery, your session should look the same as it was the last time the recovery file was synchronized. All unsaved edits should still be present.
Click the Continue button. Source Insight will continue to start as though no recovery were done. You will not be able to recover after continuing.
Click the Quit button. Source Insight will quit immediately without attempting recovery. If you run Source Insight again, it will still be able to do the recovery if you want to.
When a recovery is performed, Source Insight will resume as though you were in the middle of an editing session. All the previously opened files will still be open and any edits you made will still be there. After the recovery, you can continue to edit normally, or you can quit and save each file that had changes. Use File > Save All to save all recovered files.
Before a recovery can take place, the recovery system requires that the original files you had open previously must still exist, and be unchanged since Source Insight opened or saved them. If you need to perform a recovery, you should do it right away, before any of the original files are modified.
Verify the results of a recovery before saving.
Source Insight's recovery system is very good, however, no recovery system can be foolproof. There are always windows of vulnerability. If a recovery is needed, it is probably due to unusual circumstances, such as a hardware failure, a power failure, a bug in a program that you spawned from Source Insight, or a bug in Source Insight. Whatever the reason, it is still a good idea for you to scroll through each recovered file to see that everything looks intact before you actually go ahead and save the files. If Source Insight's recovery file was damaged or not written entirely, or the failure occurred while the recovery file was being updated, then Source Insight may unwittingly trash your file while it thought it was recovering it.
If you find that the recovery didn't work correctly, do not save the file. Close the file without saving it. The original, unsaved file will still be intact, although without your last changes saved. Also, the backup feature probably made a recent backup of your file in the Backup folder.