I had Windows 7 installed on my machine, then installed Ubuntu completely separate (didn't use Wubi), and now I would like to remove Windows without erasing my harddisk and reinstalling Ubuntu. Is there a way to do this? (I am currently running Ubuntu 12.04)
Since you evidently have Windows and Ubuntu installed into separate partitions, the easiest way to get rid of Windows is probably to open GParted and reformat - or delete - just the partition containing Windows. This will not affect your Ubuntu intallation, so there will be no need to reinstall it. When you reboot, run
to make sure that it is updated to no longer show an option of booting into Windows 7.
So, after having done these things, you'll have a partition that used to contain Windows, and another that still contains Ubuntu. Now, if you want to make it all one partition, you'll need to boot from the LiveCD so that you can run GParted on the Ubuntu partition, too. You can choose to move the Ubuntu partition to the left (because it is likely your Windows partition was one of the first partitions) and expand it to include the entire hard drive.
have you tried opening the disk utility .... hit start type disk press enter .... find the disk .....find the win 7 partition on the disk ....delete/reformat the PARTITION, not the Volume. (It wont/shouldnt let you format the vol when your running it anyway) ....then reformat the partition to ext4 and extend your disc ....or just set it to auto mount and use it for file storage ....Its proly safer to keep the partitions separate anyway in case something happens to one you wont lose the other ....I prefer keeping my OS on a partition and all the files on another on the same disc ....this way i yank or break my OS whenever I want without worrying about my precious content.... Its the way safer way to go .
Alternatively mount the windows partition use sudo and -R (recursive) and delete the contents and just use the disk as normal