1. No its not designed that way. The unit is serviced and assembled so that all the parts go in 1 side.

2. The fan is not shown in the 755 manual but it is on other manuals.

How this is done is NOT one way works for all.  Depends on WHICH MODEL.

DO NOT Flood the motherboard with rubbing alcohol.  Cleaning of the Heatsink or cpu should be done OUTSIDE the case away from the motherboard.  Either the alchohol or the heatsink compound will short out the motherboard.  There are 2 captive screws that hold the heatsink in.  You loosen those and ROLL Back the heatsink and then lift out.  The Fan is behind that.

1. Rotate the heat sink assembly upward, and remove it from the computer.
   Lay the heat sink down on its top, with the thermal grease facing upward.
   
   

Its Similar to this but not quite.  The Principle is the same though.

Removing the Fan Assembly

1. Follow the procedures in "Before You Begin."
   
   
2. Remove the computer cover.
   
   
3. Remove the heat-sink assembly.
   
   
4. Press the release tab on the fan-cable connector on the system board to remove the connector.

Dell™ OptiPlex™ 755 User's Guide

semichman

There are four different versions of the Optiplex 755, which version do you have?

The optiplex 755 User's Guide, is here:

<ADMIN NOTE: Broken link has been removed from this post by Dell>

Bev.