One day, I wanted to format my pc with Windows 7, but when formated it, it got two windows 7, one on each disc partition. Now, I want to format the pc and delete both windows 7, but I want to save one of the partitions... How can I do it?
Assuming you have a windows 7 install disk/media probably your easiest method would be to back up or save whatever it is you want saving in the partition and then boot from your actual windows disk. That will mean changing your boot order via the bios so that either DVD or thumb drive (or whatever you have windows media on) is first.
Choose custom install and that will give you the options on whether to remove or keep whatever partition. Just remember though that anything in that partition will be written over when you install windows which is why I mentioned the back up above.