How to replace an optiplex 170l cpu

Updated April 17, 2017

The central processing unit (CPU) installed in your Dell Optiplex 170L desktop system is the main component that controls the computer's speed. During the life of the computer there will undoubtedly be new software released that may push the processor to its limits. If your programs are running slowly or take an unacceptable amount of time to install, you can get a big increase in speed by replacing the CPU.

Shut down your Dell Optiplex 170L. Unplug the power cable from the back end of the case and remove all of the remaining cables from the monitor, keyboard, mouse and other devices.

Place the Optiplex 170L on its left side so that the access panel is visible. Push in the latch on the back edge of the panel and grab the two indents. Slide the panel off the Optiplex computer case.

Locate the cooling fan at the centre of the Optiplex motherboard. Unplug the cable connecting the fan to the motherboard.

Pull up the plastic airflow shroud on the side of the cooling fan to reveal the CPU's metal heat sink. Twist the shroud clockwise to lock it in place above the fan.

Press down the green securing tab on the side of the heat sink. Grab the base of the heat sink and lift it upward to remove it from the CPU. Set the heat sink aside, with the thermal material facing upward.

Locate the plastic release bar on the right side of the CPU socket. Lift the bar upward to unlock the CPU from the socket. Grip the edges of the CPU and pull it straight upward off the motherboard.

Line up the pins on the bottom edge of the new CPU with the holes on the motherboard socket. Push the CPU down into place and then push the release bar back into the lock position.

Reassemble the heat sink, airflow shroud, cooling fan cable, side access panel and power cable. Turn on the Optiplex 170L computer.


The Dell Optiplex 170L motherboard is compatible with either Pentium 4 or Celeron processors that use the Socket 478 technology. You can find Socket 478 processors through online stores that sell computer parts. Before replacing any computer parts, you should save any critical files you need to an external source in case any components are damaged while you are working inside the computer.


Do not directly touch the bottom end of the CPU's heat sink and do not set the heat sink face down when you remove it from the motherboard. If the heat sink comes into contact with foreign material, such as the oil in your skin or dust particles, it will not keep the CPU cool. Static electricity can damage the new CPU before you install it in your Optiplex. To keep your CPU safe you need to ground yourself by touching the exposed metal tabs on the back end of the computer case.

Things You'll Need

  • Phillips screwdriver
  • Socket 478 processor
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About the Author

Ty Arthur has been writing technical and entertainment-related articles for a variety of online sources since 2008. His articles have appeared on and many other websites. Arthur attended the Great Falls College of Technology and studied both computer science and creative writing.