XBOX 360 Controller On PC

[[TC] Viper]

I was getting the same thing with the lights going on for a split second then turning off.
In Device Manager, it kept coming up as an unknown device. I tried it in 2 other PC's and was getting the same problem.
If it's brand new, get in contact with the outlet you purchased it from, that's assuming the warranty is in good order.

All i can suggest is to try another 360 pad in your PC or try your pad in another PC.
Other than that, i'm out of ideas.