How to restore my old Iphone 3gs to Factory Settings?

Okay so I just recently got a new phone and have sold my iPhone, but now I need to restore it… I can't do it from the phone because of a restrictions pass code that I can't remember because I had the phone for 3 years; and I can't do it from the computer because of some disc or something but I tried twice and both times it said there was a problem… Please help me so I can send this phone out!

Okay so this will restore it right back to factory settings, the professional way.

Hold Home and power buttons for 10 seconds - Exactly ten seconds, not just till it goes off…

Keep Holding the home button but remove your finger from the power button and hold for 7 seconds…

Then plug into iTunes, and it will ask to restore it. Follow the prompts, and you'll be right to go!

  • Will i lose my iphone contacts if i restore to factory settings? I have to restore to factory settings because of a really annoying problem related to downloading apps, will i lose my contacts if i restore to factory settings?
  • My iphone wants to restore to factory settings? Question is should i do it? it states it will erase all data and update so i'm not sure if i want to risk it incase it worsens the situation. i've updated itunes and tried again with no luck. Its annoying as i can't sync any cds onto it and it can't update… Is it worth the risk? Or should i just leave it and keep it as it is as i have no other problems with the phone.
  • My iphone 3gs won't restore to factory settings? I bought an iphone 3gs for $50 from my friend, it worked fine except i had to restore it. It automatically updated the IOS but when it finishes restoring it gives me a message that says something like: "itunes could not restore your device due to an unknown error(-0)." any idea on how i can fix it? Or does this mean my iphone is obsolete and will no longer work?
  • IPhone Spyware: Restored from backup. To late to restore to factory settings? Believe an Ex jailbroke and put spyware on my iPhone. Connected to my computer and iTunes but restore from a backup not to factory defaults. Concern is that if I do so now, is my computer and the restore already corrupted? Does iCloud make a difference?