I'm using CorelDraw X3. Through it I can't correctly open my file, I see unknown image instead my graphic.
There's not so much you can do with X3 and earlier. X4 onwards are stored like zip files and you can often use a zip viewer to extract the graphics from them, but with X3 there are less options.
Both of those you can verify if you open it in a hex editor such as PsPad and look at the top of the file:
Riff and CDR will confirm it is a CDR file and D will confirm it is version X3. If you don't have a hex editor you can open it in notepad -- it will (eventually) show you the top of the file, though not neatly laid out like the above.
PK as the first two characters means it is a zip file -- possibly X4 or later, but it could also be another type of zip file.
If it is an X3 file, some things you could try:
But first look in the same folder to see if there's a file named backup_of ... or autobackup of ... and search the machine for crash files ending in .cor -- any of which could possibly be an earlier version of your file.
Make sure that automatic back-up is turned on/active
If Make Back-up on Save is not enabled and the application becomes unstable and closes down, you may be able to find a .tmp file or cdr file that could have your data in it. If you are attempting to recover a file from CorelDRAW X6, simply rename the .tmp extension to .cdr
Or you may use CorelDraw Repair Toolbox if these tips weren't effective
http://www.coreldraw.repairtoolbox.com/