Reprogramming a Microcontroller
The Arduino Uno is an Atmega328p AVR microcontroller in DIP package. If you can find one of those in a piece of equipment, then using it as an Arduino is as easy as hooking it up to the right ICSP header and using a in-circuit programmer.

I'd put the chances of finding a DIP AVR microcontroller in a random piece of gear at around 0.001% or so. Buying the $2.50 part from Digi-Key seems like a better way of going about finding one of those. Also, if the kind of microcontroller is any other kind (8051, PIC, ARM, 403, etc) then Arduino compatibility isn't going to happen.

Most if not all electronics made commercially in the last 10 years or more uses mostly surface mount technology. This not only makes large-scale assembly easier and cheaper, but it also saves on size and materials, which leads to lower cost. Surface mount chips are notoriously hard to de-solder and re-use for anything, requiring at a minimum a good workstation setup with hot air rework capability and good flux and de-solder braid, as well as some new carrier board to mount the device on, as it won't plug into a breadboard like a DIP part will.