I have trouble with my ipod mini 4GB. Here the scenario first when i charge my ipod it plays normal like i could play music and games.And when i take off the charger it's dead.I don't have a money to buy anything new.thanks guys help me please

The most likely cause is a worn out battery that cannot hold a charge. When it is connect to USB, it gets power from that connection so it works as expected. When you disconnect it, the battery cannot hold the charge for more than a few seconds, and it dies.

Having the battery replaced by a shop is likely to not be economical for an old iPod mini, compared to the current gen 16GB iPod nano that is available on the Apple refurb page for $99

http://store.apple.com/us/browse/home/specialdeals/ipod

If you are good at fixing small electronic devices, this web site has repair guides

http://www.ifixit.com/Device/iPod_Mini

(It is not designed to be taken apart by the user.)

The part is available on eBay and other online sources.

NOTE: The tiny hard drive in the iPod mini is supposedly compatible with a standard compact flash card, including much higher capacity than 4GB.

http://www.instructables.com/id/Upgrade-Your-iPod-Mini-With-Flash-Memory---No-Mo re/