if you have an iphone4 that wont boot up because the battery went dead or u switched it off and tried to switch it on, Its most like because the iphone's software version is 4.3.4 or 4.3.5 and it has been jailbroken(that is cydia has been installed). The jailbreak for 4.3.4 and 4.3.5 are tethered which means it wont boot up unless u connect it to a system and run some files and programs. For some people, this can be frustrating and unfortunately some bought it like that not knowing the implication, some sellers in ikeja will sell that type of iphone4(unlocked with a chip) and tell u never to switch it off( although its far cheaper). its because they didnt activate it thru itunes. Instead they used the jailbreak to hacktivate it, unfortunately the jailbreak is not a full jailbreak. If u want to remove d jailbreak and be able to switch on and off the iphone4( even if unlocked with a chip), u will need to restore and activate the iphone thru itunes. If u av d official sim that d iphone4 is locked to, use it to activate the fone thru itunes but if u dont av the sim BUT u are sure of the network its locked to(by using SAM in cydia), u can bring it and i will use my global activation sim to activate for u. if u dont know d network that its locked to (after trying all means possible like SAM etc) then i will use d network finder ( THIS PART IS NOT GOING TO BE FREE), to check the network, i will now activate using the global activation sim. After all these steps, u will now be able to use your iphone without d need of a tethered jailbreak and switch off/on your fone anytime u want.