help me out .i was given toshiba satalite c50..it came with window 8 .... when it was given to me at first.i charged it for 30 mins while window 8 was installing...after a week i crashed the OS.....when windows 8 was active the battery last 10min..but i later installed window7..to my suprise win7 usually advise me to change battery.my pc battery no longer last than 5mins..and it does not fully charge before it says it full...i removed it again , then it lasts three minitues.help me how can i revive it.