I'm busy fixing 3 machines at the same time and I needed to swap a CD drive in my brand new system. I power down the machine that I want to swap the drive and remove the old drive. I then, for some unknown reason power the machine up (with no drive). I go away for 10 mins and I come back and begin plugging in the IDE and the power cables, but hold on... nope it's too late... I've already plugged the cables in (while the PC was on) and I just clean forgot, whoops. I didn't notice the fans spinning because the system is pushed in the corner as the wires are tight so I just squashed my arm in and because I've got other machines running I didn't hear it on (it runs quiet anyways). When I half-plugged in the power cable, the whole system juddered for a second as if I just turned the power off but windows was still on and it seems ok. I just want to know if I could have damaged anything (the mobo or the power etc) by accidently attempting to plug in hardware while the PC is still on. I am planning on leaving this PC on 24/7 as a download box and I don't like the thought of the power supply packing in because I've been an idiot. Has anyone done this before? Does it cause any damage? Thanks in advance, Scott.