Edit Track Points

On your PC, right-click the .GPX file and choose "open with" and "wordpad". This is the standard windows text editor - any other text editor will do if you prefer. Briefly study the layout of the file - you will notice that a few lines repeat for each GPS point, with the same variable names and different values. Find the GPS co-ordinaes for the end of your hike, and simply delete the points below that, making sure you delete exact multiples of the repeated sequence of variable names. Save the resulting file under a new name (i.e., don't overwrite the original downloaded file) until you verify that the new file works correctly.