Dell OptiPlex 170L - Manual (Page 111)

4. Ensure that the jumper setting on the new drive is set for "cable select" (see the documentation that came with the drive for information).
5. Remove the two extra alignment screws from the front of the computer and insert them into the drive.
6. Gently slide the drive into place.
7. Once the drive is in place, gently apply pressure to ensure that the drive is fully seated.
8. Use the securing screw that came with the drive to attach the drive to the computer.
1 drive alignment screws (2)
NOTE: Some computers come with only two extra alignment screws; others come with four. You only need two alignment screws for this procedure.
1 securing screw
2 drive alignment screws (2)
3 extra alignment screws (2 or 4)