I brought a 128gb 13 MBA - its fine except i feel better with a bigger drive - my fault. So know i need to erase the drive and swap it for a 256gb. Just brought it today and i want to exchange it tomorrow (+£250!! for extra 128gb.... ) Anyone give a me a quick heads up on how to do it. Ive done a few searches and it seems i restart and press the option keys and get the recovery hd option thing and then i do an erase from disk utility at top and then download 4gb of lion (!!)..... Help appreciated. A nice precise concise web link would be great. Thanks.