Most USB devices drivers automatically installed after you plug in on you PC. Most of use call it "Plug and Play". For example if you plug a USB mouse into your USB port windows automatically searching and install the appropriate driver. You will see a dialog box like this:
STEP HOW TO INSTALL USB DRIVERS.
1. First identify what is your device model number/type name. For example you are using Verizon broadband modem UM150.
2. Go to the official download page and download the correct driver that match your USB device model.
3. Install it and allow few minutes for windows to fully updates and identify all components for the USB.
Certain USB devices come with firmware CD and you just need to install it on your system.
USB DRIVERS FOR USB FLASH DRIVE AND EXTERNAL STORAGE
Windows already have the generic drivers for USB FLASH DRIVE and MEMORY CARD. Normally it is called "Mass Storage Device", by default all windows operating system have this driver in thier system, if not you can get it from Microsoft site here: http://support.microsoft.com/kb/318812
This apply for most external device such as:
external magnetic hard drives
external optical drives, including CD and DVD reader and writer drives
portable flash memory devices
adapters bridging between standard flash memory cards and USB connections
digital audio players and portable media players
For memory card if you get an error "Disk Management Console View is not Up to Date". I already write a post to solve the problems in details here. http://laptop-driver.blogspot.com/2010/12/disk-management-console-view-is-not-up.html
WHAT IF THERE ARE NO DRIVERS OR FIRMWARE AVAILABLE.
1. Try to plug the USB device into other USB port.
2. If the problem persist, open device manager and expand the USB Root Hub
4. Right click on it and select Uninstall. Reboot your computer.
5. Open device manager again and right click on of the any USB root hub list and select scan for hardware change.
USB SUDDENLY STOP WORKING
1. Turn off your computer.
2. Deatch power chord or power supply.
3. Remove battery (for laptop)
4. Open your computer and plug the USB device.
Sometimes when the USB is too hot and too busy windows will stop the USB device to prevent from system instability. I already experience this with few device from HUAWEI which require me to unplug and replug every time it is not responsive. Later on i solved the problem buy put a small fan near the USB device to keep the temperature low.