one of computers won't recognize external hd

I have a Buffalo Ministation usb 2.0 ext hd, HD-PX500U2 that I got from a friend. Has been working fine for weeks. Now it won't show up in My Comp on my desktop or laptop. Does show up on a friends desktop, no problem. Desktops are WIN XP and laptop is WIN 7.

 

Lo and behold, after about 6 reboots of my laptop it now shows the Buffalo. Still no show on the XP.

 

Plug something else in the port you normally use, like a flash drive. Configure for the device, then shutdown, remove the flash drive, then try your drive, preferably in a different USB pair.

Also, note the ATX Form Factor standard for PSUs requires all ATX compliant PSUs (that's about 99.99% of them) to provide +5Vsb standby voltages across several motherboard points when the computer is turned off, but still plugged in (and if equipped, the optional master power switch on back of the PSU is set to on). This standby voltage is there to keep several circuits "hot" or "alive" while the computer is off for such "Wake on..." commands as Wake on LAN, Wake on MODEM, Wake on Keyboard, and Wake on Mouse.

Especially with legacy hardware and operating system, it is often necessary when trying to get new (or new again) hardware recognized, not just to reboot, but to shutdown, and unplug from the wall (or set master power switch to off) for about 30 seconds to ensure the +5Vsb voltage is removed, and no settings previously being held by it are still being retained. Then reconnect and boot and see if your hardware appears. For a notebook, you need to make sure it is totally shutdown, and not in a hibernate sleep mode. That may require unplugging the power supply and pulling the battery. However, later versions of Windows, especially W7, are much better at properly recognizing USB hardware changes - USB is supposed to be hot-swappable. Some systems (and individual devices) are better at it than others.

Finally, it is critical with every USB "storage" device - not just flash and external hard drives, but phones, GPSs, cameras, MP3 players, that you either wait until prompted before removing your USB device from your computer, or you ensure the "Policies" property for the device is set to "Quick removal ". But even with quick removal, the hard drive needs a bit of time to allow the R/W arm to "self-park" to a safe spot while you carry the drive about. So count a long 3 before disconnecting.

If you need write caching enabled (for better performance), then you must wait until prompted to disconnect.

I do note your modern version of the "sneakernet ". In the olden days it typically referred to floppy disks being moved from one computer to another by someone hand-carrying the disk from computer to computer while wearing sneakers. It was the first method of malware distribution and it was, and still is a most excellent method of malware distribution.

So forgive me, but when I hear of storage devices being shared in this manner, I get concerned with security. Unless you have total faith your friend's security awareness and discipline at "practicing safe computing" with EVERY computer used with that external drive (and anyone else who might have used it) then I would urge you scan your system(s) now with all you got - especially your legacy XP systems.

And the same advice goes to your friend. Unless he knows for a fact your computers and your network (everything on your side of your gateway device, typically served by your Cable/DSL modem) are totally secure, he should scan his systems now.

Practicing safe computing means keeping our systems patched and updated with the latest critical updates, scanned with a current real-time anti-malware solution, and blocked behind a firewall - plus avoiding risky behavior like filesharing tunes and movies via torrents or P2P sites that support illegal filesharing.

If any of these computers are used for banking, on-line shopping, or important work or school project, there should be no emotions involved or hard feelings taken. It's just like washing up before handling food.