The most common problem people have is when they connect a USB flash drive (sometimes called a thumb drive) to a computer and the computer doesn’t recognize it. First, let me say that these are great devices. Connect one to your computer and it works like a removable hard drive. When you connect a USB device to a computer running Windows XP, the computer will detect it immediately. When that device is a USB drive, you’ll probably see a message on the taskbar that Windows detected a new device, followed by a dialog box that asks if you want to open the drive to see its contents, play a movie and other choices.

Windows will also assign a drive letter to the device. But sometimes you won’t get this dialog box, and when you open My Computer manually (Windows key + E), you won’t see the device listed. That means there’s a drive letter conflict.

Here’s how you fix it:

1. Select Start/Control Panel, then double-click Administrative Tools.

2. Double click Computer Management.

3. On the left side of the Computer Management console, select Disk Management.

4. On the right side, you should see a device listed as a removable drive, probably with the same letter as another drive you’re already using.

5. Right-click the white bar where it shows the letter, then select Change Drive Letter and Paths.

6. Select the letter, then click the Change button.

7. Pick a letter not already in use from the list, then click OK. Click OK on the warning message, then click OK again. (I assign U: to all USB flash drives, since I never use more than one flash drive at a time.)

8. Close the Computer Management console. When you go back into My Computer, you should see the USB drive with the new letter.

Another common problem is running out of ports. When USB started being implemented, the idea was that you would daisy-chain the devices together. So computer manufacturers would put in only two ports (always in the back) and only one port on laptops. For a variety of reasons, the daisy-chain idea never caught on, and computers made today typically have four ports in the back and two in the front, for quick access.

If you run out of ports, you can fix the problem as with so many others by applying cash. Buy an external USB hub for anywhere from $10 to $40, depending on size, number of ports and power. A hub will split a single USB port into several more. The better ones have their own power supply, so your devices don’t have to rely on the computer for powering the USB connection. When there isn’t enough power to go around for all the devices, they can go offline.

This brings me to the last problem I’ll discuss today: USB devices going offline because of reasons unrelated to power shortage. This was fairly common when you had many devices connected using USB 1.1 in versions of Windows older than 2000, where the devices had to supply their own software to get USB to work. (Native USB drivers were first included with 2000, then made more robust in XP and Vista, presumably). If this happens, simply unplug all the USB devices, then plug them back in one by one. If any are daisy chained together, connect the parent devices before connecting the child devices.