DETECTION OF THE ARDUINO BY THE COMPUTER

Hello there,
I'm really new to the Arduino world and I for one have an Arduino Uno I purchased recently. The first day of trial was a success and it was in perfect condition as I was trying out some simple projects majorly to deal with LEDs. But the sad part of it was that the following day, the computer could no longer detect the Arduino. It's only the two LEDs, "ON" and the one at pin 13 that light. This has greatly put me many steps behind and is crashing my morale. The computer am using runs on windows OS and even when I tried it on my collegues' computers, it was still not detected. At this juncture I'll be grateful for upon any ideas you are willing to share with me to help me out. Thanks alot.

If the card is a clone: which USB-driver chip? (which card)
also: Try a second USB-cable - before contacting seller for replacement..