How do I know Ubuntu and Windows7 are installed in different partitions? I want to remove windows7 and keep Ubuntu13.04
By default, ubuntu is installed to an Ext3 or Ext4 partition, as well as the boot partition and the swap space, which will be marked as such.
Windows 7 must be installed to an NTFS partition, in which case any NTFS partitions likely contain your Windows 7 installation, along with the system partition used for boot and any OEM recovery partitions.
As Ramhound mentioned, you should check the contents of the partitions before you delete them. This can be done by simply mounting the partitions and opening them in Nautilus. Back up anything you don't wish to lose.