Call me out on it if you think any of what you're about to see is sacreligious, but be assured now that all of the machines in question were not in a state where they could be repaired to working condition feasibly.
First up is an IBM. Not a valuable IBM like a PS/2 or an XT machine, but an Aptiva 2176. It was originally a Pentium 166, and its mainboard was completely non-functional. I was in need of a spare machine and decided it would be the first in what ended up being a few rebuilt vintage boxes. The 2176 like most OEM boxes at the time used the LPX form factor, but with an alternate riser to most makes. So I got to measuring and cutting...



MicroATX'd! Now the IBM was ready for action. I actually had another IBM at home just aching to donate its componentry, a far more modern NetVista P4. Once complete, the Aptiva looked something like this... (clickable links to big pics!)



Functional AND retro, all at the same time! The IBM is now for sale as it's no longer needed - it was primarily a media machine for in the bedroom, its duties now being handled by an Intel Atom based machine.