The number of distinct lines representing the altitudes, medians, and interior angle bisectors of a triangle that is isosceles, but not equilateral, is:

$ \textbf{(A)}\  9\qquad 
\textbf{(B)}\ 7\qquad 
\textbf{(C)}\ 6\qquad 
\textbf{(D)}\ 5\qquad 
\textbf{(E)}\ 3$
1. **Identify the properties of an isosceles triangle:**
   - An isosceles triangle has two equal sides and two equal angles opposite those sides.
   - The altitude, median, and angle bisector from the vertex angle (the angle between the two equal sides) are the same line.

2. **Count the lines for altitudes:**
   - In any triangle, there are three altitudes.
   - In an isosceles triangle, the altitude from the vertex angle is the same as the median and the angle bisector from that vertex.
   - Therefore, there are only two distinct altitudes from the base vertices and one from the vertex angle, making a total of 3 distinct lines for altitudes.

3. **Count the lines for medians:**
   - In any triangle, there are three medians.
   - In an isosceles triangle, the median from the vertex angle is the same as the altitude and the angle bisector from that vertex.
   - Therefore, there are only two distinct medians from the base vertices and one from the vertex angle, making a total of 3 distinct lines for medians.

4. **Count the lines for angle bisectors:**
   - In any triangle, there are three angle bisectors.
   - In an isosceles triangle, the angle bisector from the vertex angle is the same as the altitude and the median from that vertex.
   - Therefore, there are only two distinct angle bisectors from the base vertices and one from the vertex angle, making a total of 3 distinct lines for angle bisectors.

5. **Combine the distinct lines:**
   - The altitude, median, and angle bisector from the vertex angle are the same line.
   - The altitudes, medians, and angle bisectors from the base vertices are distinct.
   - Therefore, we have 1 line from the vertex angle and 2 lines each from the base vertices for altitudes, medians, and angle bisectors.

6. **Count the total number of distinct lines:**
   - From the vertex angle: 1 line.
   - From each base vertex: 2 lines (one for each base vertex).
   - Total distinct lines: \(1 + 2 + 2 = 5\).

Conclusion:
The number of distinct lines representing the altitudes, medians, and interior angle bisectors of an isosceles triangle that is not equilateral is \( \boxed{5} \).