Sheilding

There has been discussin on the shielding of the motor cables but I'm
wondering what else should/needs to be sheilded as well AND why?

What is/are the source(s) of the offending iterference? What ,if
anything, can be done at the source to reduce the interference?

I ask becuase I am 95% finished with my controller/PC which are
housed in the same case. The motor phase cables are sheided. The
step, direction & 5v cables between the Gecko's and break out board
are sheilded and the home & limit switch cables are shielded. This
leaves the Gecko power lines, PS lines, 115v lines, parallel ribbon
cable from the breakout board to the moher board, PC power supply
lines, floppy drive and IDE drive cables unsheilded.

What should I be concerned about?

Thanks

Jay