Computer won't recognize any USB devices

[bigmike991]

Hello, I really need help with this.  I just bought a external harddrive and my computer won't recognize it.  Here is the background:

My fingerprint reader and printer worked fine through USB.  I plugged in my external HD and my computer would not recognize it.  I read up on it and it said try unplugging your other USB devices.  I unplugged all USB devices (except keyboard/mouse) and plugged in my external HD.  My computer recognized it.  I go to plug in my external HD again a few days later and it will not recognize it anymore.  Now, when I plug my other USB devices in (fingerprint reader/printer), my computer will not recognize those now.   Does anyone know why my USB's are acting up like this???  I could not find this problem on the forum.

Thanks!

Mike

[2k_dummy]

Get an externally powered USB hub.

[bigmike991]

But I really don't think it is a power issue because they all worked fine at some point.  My computer just won't recognize anything anymore. 

[bigmike991]

Nevermind...they seem to be working again.  I just don't know why they work when they want to.

Thanks!