I'll say upfront, I've never used the WD backup software or Seagate for that matter, I prefer to know what I'm doing!
I also assume you have never disconnected your external drive incorrectly - you must always either use the eject tool in Windows AND wait for the Safe to Disconnect message or, if Windows thinks the drive is in use, shutdown Windows. Just unplugging the drive without using these methods can leave buffered data not written back to the drive and if this happens to be a control table, your files disappear.
Also some disk partition management tools can destroy data - one such is Partition Magic, which will wipe an NTFS-Extended partition if you attempt to move it. But from your question, I don't expect you use such tools.
I'll take your request at face value, if this is over simplistic, I apologise.
First thing to do is open Windows Explorer, or File Explorer if you are unlucky enough to have Windows 8! Then in the left column, look in the Computer section (you may need to click the arrow to expand it). That will show all the disks Windows knows about. You will obviously have your system drive and any other drives inside the physical machine. At the end, you will see the removable external drive or drives. If there are more than one and this is the only thing you have plugged in, then the external drive is partitioned, if there is only one, it isn't.
Now for each of those removable drives, right click and in the menus that shows up, click Properties. This will tell you how many folders and how many files are on the drive. If they are all zero, then nothing got saved - or the drive got corrupted. But if there are folders, click the arrow to the right of the drive letter and left click on each of the folders in turn - you should see any files that exist on the drive.
If you still can't find any files, you probably need to look at the drive with something like Gparted from a Linux live CD or from the bootable version (free download) of Partition Wizard - NOTE - NOT PARTITION MAGIC! I would guess from your question that these tools may be a little outside your level of expertise, in which case, I advise seeking help form a more knowledgeable friend or colleague. These tools can be very dangerous!
If the disk has been corrupted by incorrect removal, it may be possible to recover the files with a Linux live CD (it's rather more forgiving than Windows) or to repair the disk with one of the disk doctor tools available - again, I would advise you to seek help if you go down this path.