Asking for a friend, My friend has been using a 250GB hard drive but very recently aquired a 500GB but is now looking to clone all data and partitions from the 250GB hard drive to the 500GB hard drive.
I presume this 500gb hard drive is actually an Xbox 360 hard drive? or is it just a random PC hard drive? If the old 250gb hard drive is one for a phat 360 you can use the data transfer cable on the Xbox 360 its self and just copy all the content from one drive to the other under Settings > Memory
Both drives are official Xbox 360 HDDs, both are for the slim model. She doesn't have an official Xbox 360 transfer cable. Best advice I could give was copy/paste everything from 250GB to pc and transfer to 500GB using Fatxplorer or a data recovery program. I can't guarantee either way will work, worst case scenario she has to replay everything her new HDD
Another thing I can suggest is she could configure a USB memory stick to be used as Xbox 360 storage then copy things over to that, swap out the hard drive and copy things back to the new hard drive. Re playing everything is a bit extreme, saves are pretty small so easy to copy over.