I have three partitions on my HD at the moment, and I want to create just one HD by unpartitioning.
However, I don't have a separate hard drive or USB or anything that could hold the amount of stuff I have, so I was wondering if it's possible to unpartition in Disk Utility without backing up my files?
I really hope so, because I can't really be bothered backing it up...
Deleting a partition will erase its contents. If you don't currently have enough free space on the first partition to hold the entire drive, you must create a backup. Even if you do, you should create a backup, as that drive may fail at any time.