Important: Before you delete a partition, please know that all data on that partition will be erased forever. By all data I mean all data: the operating system itself, all installed programs, all saved documents, movies, music, etc. that might be on that drive. It's assumed that, by this point, anything you wanted to keep you've backed up elsewhere.
Highlight the partition you want to delete and then click or touch Delete.
Note: Your list of partitions may differ considerably from mine, which you can see in the screenshot above. I have one 60 GB physical hard drive on my computer that I previous had Windows 8 installed on. My primary partition, which is the C: drive when I'm logged into Windows, is 59.7 GB. That other small partition (350 MB) is a supporting partition that I also plan on deleting, which we'll get to in a few steps.
Warning: If you have multiple hard drives and/or multiple partitions on any of your drives, make sure you're deleting the correct partition(s). Many people have second hard drives or partitions that they use for backup. That's not a drive you want to be deleting.