If you want to image the contents of the 20 GB drive onto the 30 GB one, there're numerous programs that will do that. One would be Norton Ghost, another Easeus Todo Backup Free which you can download from
http://www.todo-backup.com/products/home/free-backup-software.htm . The Easeus program is free.
Now I have to make a couple of comments. You didn't say what OS you're talking about but 30 GB is far too little space for any current version of Windows. When you can buy far larger hard drives for $50 or less, that might be something you should investigate. Next you have two hard drives and say you want to delete a partition. Are you trying to make 2 drives look like one? No hard drive is accessible without at least one partition, so if you have two hard drives, you've got to have a minimum of 2 partitions. Is there some 3rd partition somewhere you want to remove? Not knowing what OS and what you're trying to delete, it's very difficult to tell you how to proceed.
Recently I've aquired a second hand desk top PC that I'm doing up for my son. It has 2 hard drives in it, a 20gb and a 30gb. I've reformatted the 30gb drive with the OS, and want to use the 20gb as extra storage. The problem is that the existing operating system is on the 20gb drive, when I try to format the drive, it says that it's unable to complete the format. I've tried to remove the partition by right clicking my computer, going to manage, disk management, etc, but it doesn't allow me to remove the partition. Any ideas please.