|You don't need to re-install the operating system, if some USB devices are working fine.|
The drivers for USB 1.x are installed automatically by the operating system.
The drivers for USB 2.0, if your mboard supports USB 2.0, are built into Windows 7 , but the main chipset drivers for your mboard must be installed, in order for the USB 2.0 support to be installed in Windows.
You probably need to plug the external drive and/or the bluetooth dongle, or both into different USB ports than you have them in now.
Troubleshooting USB device problems including for flash drives, external drives, memory cards.
See Response 1:
Check that out first.
Rarely, not all the ports on the back of a desktop case may be able to supply 500ma each.
If you have a desktop computer, Note that I answered a Topic on this site recently where a guy had an external drive, which does require the full 500ma, connected to a port on the back of a desktop case - it would not work properly when a webcam was in the port next to it, but it worked fine when the webcam was unplugged. Ports on the back of a desktop case often have two ports connected to the same USB controller module that are ports one above the other - you could try connecting the cable to one of those and leaving the other un-used.