What does it say in device manager? Any problems there? Have you installed the chipset drivers for the laptop after the reformat? I think its just a loose connection causing the problem. Heres a website on USB ports.http://pinouts.ru/Sl...SB_pinout.shtml
Now i have used a old mouse USB connector, with the ends stripped, to test a USB port for power (they always seem to work when i test with a multimeter). It also may be that your USB port does not have enough power for a webcam. Each Port has 500 milliAmp output( 1/2 amp). On my USB laptop external drive i have to use 2 USB ports for power, even tho the laptop drive is only rated a 500 milliamps for power. It seem the initial start of the drive takes more than the 500 milliamps, so the drive would not start most of the time.
Heres a picture of my External drive USB cable.
Maybe one of these ideas will help.