Unlock Iphone 4

[Nezzz]

I bought a second hand iphone 4 but when i go to reset to factory settings i'm asked for a 4 digit passcode that the seller can't remember. Any ideas for a way round this? There's no passcode required to get into the phone, only when trying to reset.

[Milvus]

Unless your seller can remember the number you are going to have some problems. You might try forcing it into recovery, follow these instructions carefully: http://support.apple.com/kb/HT1808

[johnsonjack575]

press home key +power key button at same time for 10 seconds then leave power key button,without releasing the homme buttom you will get in the DFU mode then connect it with itunes an d restored it