I moved from a Windows PC to an iMac three years ago. For the transition I installed Boot Camp and set up 250GB of my drive for Windows. I no longer need the Windows partition. How do I delete it?
Via the internet
Dispatching a Boot Camp partition is easy. Make sure that no user accounts other than your regular administrator account are logged on. Also, if you want any of the data stored on the Boot Camp partition, now’s the time to back it up. (Time Machine doesn’t back up Boot Camp partitions.)
Launch Boot Camp Assistant (found in /Applications/Utilities), click the Continue button in the first screen, select the Create Or Remove A Windows Partition option in the next screen and click Continue again. Select the drive that has your Boot Camp partition, enable the Restore Disk To A Single Mac OS Partition option, and click Continue. You’ll be prompted for your administrator username and password. Click OK and Boot Camp Assistant will restore the disk to a single Mac OS partition.