My sandisk sansa 2g wont turn on with out being plugged in at tha computer n seems to be fine when its plugged in but when its unplugged it wont work! the battery is on a full battery but wont turn on at all! help!

Read this. Get the manual. Sansa Clip Zip MP3 Player by SanDisk

Did you run the installation CD before you plugged the mp3 player into the computer? If not, disconnect the mp3 player from computer, uninstall all the Sansa software on your computer, and reinstall the software from the installation CD.

If the uninstall/reinstall fails, update the firmware on the player from Sandisk's website.

Good luck!

-Tha Mp3 Doctor

This solution is specifically for the Sansa c200 series, but it will get you started in the right direction - check Sandisk's website for the specific method of entering MSC mode for your particular Sansa:
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

Download and install the firmware updater.
If that doesn't resolve, your player may really have a hardware issue. The battery is not replaceable by the consumer. My reccomendation is to exchange it with the store. If that fails, redeem your warranty through Sandisk (hope you saved your receipt).

-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

Download the Sansa Recovery Tool from Sandisk's website (make sure the Sansa is not plugged into the computer yet). Once the Recovery Tool is downloaded, connect the Sansa to the computer while holding in the REC button and continue to hold it even after th player is plugged in. It should go into Recovery Mode in 10-15 seconds or so.

-Tha Mp3 Doctor

Uninstall all of the Sansa software.
Go to the Sandisk website and download the clean version of the software.
Reinstall the software.
Make sure your sansa player is not plugged into the computer until AFTER you have finished this process.

-Tha Mp3 Doctor

Do a firmware upgrade, but it sounds like the hardware is probably faulty. The firmware upgrade is available from Sandisks' website. Unfortunately, if that fails it may be repalcement time.

Here is some addl info:
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

Try this: disconnect the player from the computer, hold in the volume + button, and reconnect the player to the computer while holding the volume + button in. Keep holding the volume + button for an additional 5-50 seconds. Windows should eventually go into recovery mode and revive the player- it will pop up a window that says Found New Hardware Wizard.
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Download the Sansa Recovery Tool from the Sansa website.
Format - Erases Everything: Connect your Sansa player to the computer and open Windows Media Player. Click on the Sync tab. Pull down the drop down menu underneath the Sync tab by moving your cursor over the Sync tab and left clicking on the little black arrow underneath the Sync tab. Highlight "Sansa 1GB" (wording may vary slightly), and then select "Format." - this should erase everything.
Firmware Upgrade- Erases Everything: Get the latest firmware upgrade from Sansa - it updates the firmware and erases every song in the player all at once. Note: this method doesn't work if already have the latest firmware. Go to this website and click "Firmware Updater" to find out: http://www.sandisk.com/Retail/DriverDownloads.aspx
or
http://www.sandisk.com/DriverDownload/driverList.asp
-Tha Mp3 Doctor