IBM 5170  -  Basics, for 5170 beginners

There were different models of the IBM 5170 (IBM AT).
Do not assume that what applies to one model also applies to the others.
There is no built-in SETUP (BIOS configuration) ("CMOS SETUP") to access.  Methods for SETUP are at here.
The floppy drive supplied by IBM is a 1.2M one.  Click here to read about a problem caused writing to 360K floppies in that drive.
The RAM test (and on-screen count) done by the motherboard's power-on self test (POST), excludes any expanded memory.
If your IBM 5170 has the optional second floppy drive, be aware that for the 5170, IBM marked 360K drives by placing an asterisk on the front of the drive.  (Photo)
Aged tantalum capacitors are known to explode.  That has happened to me many times, particularly when I have acquired something that has not been powered on in years.  If the motherboard, or expansion cards, are exposed to your face when you power them on, then consider wearing eye protection.  More information at here.