Do not recognized the device when I hook up to my pc .it say usb device not recognized.i have a sansa ,sanDisk1GB

reset the device to factory defaults thats it....
check your usb ports are working properly in not i recommend to re instal the usb device drivers also

Disconnect from pc, go into sansa menu to USB then press center. It's probably set to MDM. Scroll to MSC, press button. Reconnect to pc & it'll probably show up
Hope this help you

a friend told me that if the device shows as"connected" when hooked up (it does) AND the battery charges correctly (it does), then (a)the USB connection had enough juice; and (b) the PC recognizes it - i just had to FIND it. device manager/ MyComputer: nada; same for ANY file/ folder with "sansa" or "sandisk." working thru WMP (Windows Media Player), however, I discovered that drive E - for a portable hard drive, NOT currently connected via USB - was STILL showing up in the "Copy to CD or device" field. sure enough, it was the SanDisk clip player (even though it was NOT under the "Recognized Portable Devices" subsection). without using the installation disk at all, it downloaded tunes just fine. *note: the installation disk seemed to be an .exe file ONLY for the Rhapsody music service. as noted above, it was unnecessary. also - my USB ports are 1.1 and not 2.0, and package stated USB 2.0 was a "minimum requirement" - not true*

I think this is what you are asking. Forgive me if I didn't understand the question correctly.

Switch on the mp3 player. Select "Settings", scroll to "USB Mode" and make sure that "MSC", not "MTP" is selected.

When you next plug in the USB connector, your PC should recognize the Sansa as a standard USB device.

The XP did not recognize the device because I used a after- marked USB expander board that did not provide enough power to the device. Plugging to the Motherboard - attached USB port solved the problem.

Sansa c200 series – Computer/OS Not Recognizing
Connect the device to the PC in MSC Mode
View/c200: Turn on then press and hold the rewind button while plugging to the PC
If that fails, unplug the Sansa from the computer. Uninstall all the Sansa software in the add/remove programs section of Control Panel. Reinstall the clean version of the software from Sandisk’s website – make sure you get the files for the c200 series. Then replug the Sansa and try again. The root of the problem is that Sansa has one set of drivers and Windows has another. If you plug the mp3 player into the computer before installing the Sansa drivers, the Windows drivers will trump the Sansa’s.
Here is a helpful link from Sandisk on the problem with extra information on Vista operating systems:
http://kb.sandisk.com/cgi-bin/sandisk_en.cfg/php/enduser/std_adp.php?p_faqid=42&p_created=1221328944&p_sid=8VPwlRmj&p_brand=sansa&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9NzQsNzQmcF9wcm9kcz00JnBfY2F0cz0mcF9wdj0xLjQmcF9jdj0mcF9wYWdlPTEmcF9zZWFyY2hfdGV4dD1jMjAw&p_li=&p_topview=1

-Tha Mp3 Doctor

Sansa c200 series – Computer/OS Not Recognizing
Connect the device to the PC in MSC Mode
View/c200: Turn on then press and hold the rewind button while plugging to the PC
If that fails, unplug the Sansa from the computer. Uninstall all the Sansa software in the add/remove programs section of Control Panel. Reinstall the clean version of the software from Sandisk’s website – make sure you get the files for the c200 series. Then replug the Sansa and try again. The root of the problem is that Sansa has one set of drivers and Windows has another. If you plug the mp3 player into the computer before installing the Sansa drivers, the Windows drivers will trump the Sansa’s.
Here is a helpful link from Sandisk on the problem with extra information on Vista operating systems:
http://kb.sandisk.com/cgi-bin/sandisk_en.cfg/php/enduser/std_adp.php?p_faqid=42&p_created=1221328944&p_sid=8VPwlRmj&p_brand=sansa&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PSZwX2dyaWRzb3J0PSZwX3Jvd19jbnQ9NzQsNzQmcF9wcm9kcz00JnBfY2F0cz0mcF9wdj0xLjQmcF9jdj0mcF9wYWdlPTEmcF9zZWFyY2hfdGV4dD1jMjAw&p_li=&p_topview=1

-Tha Mp3 Doctor

Press and hold the lower volume button and plug it in to the computer simultaneously and keep holding the minus button until a box appears where the message of usb device malfunctioned and click on it. Then follow the instructions and it should be recognized.

it might be the USB port. that happens. try it on a different port (if you have a laptop, test it out on a friend's computer)

I agree with the above suggestion. Try setting the USB Mode under "Settings" on "MSC" on the Sansa. My computer would not recognize the e260 when the mode was set to "MTP"; works fine on "MSC".