You can explore the below mentioned VBA Code to remove lines from your word document.
First save the document in your latest Word format as .docm (Macro enabled Word Doc).
Open the dos and press ALT + F11 to access VBA Editor. From insert menu, insert a Module. Paste the following subroutine code into it
Dim H_Line As Shape
For Each H_Line In ActiveDocument.Shapes
If H_Line.Type = msoLine Then
Save the document. In main doc press ALT + F8 and run this macro.
Note that -
The macro somewhat gave unpredictable results on my Word 2013. It deleted all lines but one. Re-running the macro cleared the pending line. Secondly the macro seems to be unable to distinguish between line and an arrow. So it also deleted arrows. It did not touch other objects like inserted pictures or rectangles. This is attempted by selecting
If H_Line.Type = msoLine Then part of the code.
So before attempting anything please take backup of your original document. Also I am not too sure how old document created in Word 2000 may respond to this code, if the code would be compatible. Try it out.