Turned off my nokia 5800 and it wont come back on. when i press the power button it just vibrates..i doesnt even light up.

Ur phones firmware is seemed to be corrupted. you must reinstall your firmware from local service centres.or else if you are well expert try this out
First downloadand install Pheonix. NokiaPhoenix Service Software 2011 -Download secondly Download flash file fromthis link Nokiaflash fileand install it to C / programmefiles/pheonix..after finished thisinstallation open pheonix Inside the interfaceat the> left top File" click there and choose "open file"andthen select the approprait Product type i.e"which is written intheback banel inside the battery of every Nokia(Type RM-000).Afterdoingthis again at the left top count from "File"1..2..3..the 4th oneis"Flashing" press there when you click there you'll seethreeicon just select the "Firmware Update" again you'll seeanother interface.Look at the product code there should be blank and putyour"mouse tool" at the straight end from the "Product Code"thereis a Botton and choose the code which is written in the back sideof your phone.e.g CODE:0000000.if the same code does not found, justtake one.After this you can see "Dead phone USB flashing"clickthat box.Now this is the last stage... Connect your phone with the USBtoyour PC and let the driver install ...wait for a moment.(If yourphone working).Lastly after just finished (In case your phone isDead,unable to switch on in normal mode start from here) Connect thephone to pc without powering...insert good battery and Click the "Referbish"afterthis, a message will prompt you "press power botton"press itand wait untill the phone will Restart automatically

Chang the LCD will be work 100%