i have another computer, also WINDOWS vista, when i turn it on it runs the usual checks and stuff but it keeps shutting down after 15 seconds. it says can not detect IDE H.D.D.

Ok first off before we help can you edit your header so it's not in capitals.. I know it sounds weird but that does not help you get seen quicker. It KINDA has the opposite effect. Nobody like a person shouting..Did this just start? If so, what happened between the last time it worked PROPERLY and the first time it didn't (new hw, sw, virus, etc)?sorry.. not shouting just didnt take the CAPS off..

it was working fine and after my little brother played online games, he shut it off after that we just couldn't turn it on.

a day before this happened we also moved stuff around unplugging, replugging wires and stuff too but it was still working after all that unplug replug stuff. it just starts shutting down after 15 secs of turning it on after my bro shut it down.Open it back up and make sure that your power and data cables are securely connected to the drive and the board. Also, check your jumper settings and if your IDE ribbon has two CONNECTIONS make sure that the hard drive is plugged into the end (not the middle) connector.

Make sure that you are grounded the whole time you're working - static electricity can fry your motherboard!