When you see something like "OLD" in the data field header that usually means you are dealing with an old data field that was deleted or renamed or converted to a different question type. Rather that simply throw away the data, SSI Web will just move it to an "OLD" field in case you need it later on down the road.
Usually those fields are suppressed during data accumulation. Are you downloading straight from the admin module or trying to import a .csv file already downloaded from the admin module? If you are importing a .csv file then you can edit the file in Excel to remove the "OLD" fields, save a copy, and then import the copy without the "OLD" fields into SSI Web.