USB powered drives do this all the time. The fact they work on other machines means the fault/issue is with this PC but you didn't tell how the devices get power.
If from USB, be sure to use one of those USB Y power cables.
Bob
I have 2 external hard drives and after a trip away they do not work on my old desktop PC. They work on my laptop and any other machine I try. I reason I think it because my old pc is very old. I'd like to get the data off its hard drives(I never could get network cable to work).Other USB devices like mp3 and sticks work
My computer-Running XP pro
USB: 1.1
CPU:750 MHz, AMD Athlon
RAM 768MB SDRAM
Motherboard - AMD 750, GA-7IXE4
FSB: 200MHz
The hard drives: One is relatively new, a seagate 500GB, the other some old Freecom 250GB/music player. Neither work in this machine altought the power works for the machines when you connect them.
They also dont show up under disk management via ctrl panel.

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