I have a sandisk sansa

Can you see the MP3 player on device manager?
check -- My computer>Properties>Hardware>Device Manager> and do you see mp3 plater in Yellow Exclamatory mark (!). -----------
also try this as follows :-- be sure your player is connected to pc -- go to my computer right click>>properties> IN HARDWARE TAB select device manager>portable audio>right click select update drivers>click next>tick the option let me choose driver for this device>next choose usb mass storage driver from two options click next.this will help.---------
if in the above process the unit shoes error code 10 and nothing is happening then try this as follows :--
Open 'Control Panel' --> Open 'System and Maintenance'
Scroll down. --> Find and Open 'Device Manager' --> Find "Portable Devices", click '+' sign.
(You will see MTP with yellow '!' sign) -->Right Click, select "Update Driver Software..." ->select/click the option "Browse my computer for driver software" -->select/click the option "Let me pick from a list of device drivers on my computer" -->(there should be 2 options here) select/click "USB mass storage driver" -->click next.
This will help. Thanks please keep updated.please do rate the solution positively .thank you for using fixya.

press and hold the reset button on the player for 30 seconds to reset it to the factory defaults. Then, turn it off and turn back ON.
Next, format internal memory of the player using its own tool.

Connect the player to different USB port on the Computer and restart the Computer. This will make the Computer recognize the player.

Hi,

Hi,

Sometimes XP doesn’t properly recognize a Media Transfer Protocol (MTP) device and assigns the wrong driver, usually this is an initial ID error and it will hook a generic Mass Storage Device (MSD) driver instead or it will appear as a unknown device in device manager.

This will procedure will (usually) set the correct driver for players that use MTP so give it a try. It may fail if there are class errors in your registry but it can also (sometimes) correct them. In any case, it won't do any harm since your player isn't connecting correctly anyway.

* Plug in the player so the USB bus can see it.
* Once it’s recognized (even wrongly), go to the Control Panel and choose "System"
* Choose "Hardware" then "Device Manager" tab.
* Look for “Universal Serial Bus” in the list
* If it is, Click on it. Under that it will say either “USB MASS STORAGE DEVICE” or “Mass storage device” or Unknown Device with "?" mark.
* If it's a “Mass storage device” or "Unknown Device with "?" mark" , Right Click to get the properties.
* Choose the “Driver” tab then “Driver Details” button
* Choose “Update Driver”
* Check "Install from a list or specific location (Advanced)" and Click "Next"
* In the next window check only the "Don’t search. I will choose the driver to install” then click "Next" .
* In the next window highlight the “Portable Device” and click "Next" and browse to:
“C:\Windows\system32\DRIVERS”
* Choose “wpdusb.sys” as the driver and OK it until you see it update the driver.
In “most cases”, this will correct the problem of an MTP device being improperly recognized as Mass storage device ie, Flash Drive.

Please leave me comment, if you need further assistance
RNJ VINOD KUMAR