? i do not have a file or folder named sys.reg anywhere. where did you get it from?
to save trouble in future, try using an image backup system like macrium reflect or acronis trueimage.
if you have just deleted it and not overwritten it's disk locations, try right clicking the wastebasket icon on your desktop, select open, if the file is listed, right click it and select the option to restore the file.
you may also be able to reload a restore point (control panel - recovery) but be careful. as it will discard any changes since the last restore point while recovering and uneraseing the files.