Unable to delete .dmg files

Hello.

I just purchased a new MacBook Air yesterday, and I've been installing some new programs. For some reason I'm unable to delete the .dmg files after I've installed the programs. I'm doing it the right way by opening the .dmg file, dragging the program to the 'Applications' folder and opening the program from that folder.

The drive is not appearing, so I'm unable to eject it. This goes for all my .dmg files. When I try to delete the files, I get the message that they're still running. I've also tried to delete the programs that I've installed in order to be able to delete the .dmg file, but it doesn't help.

What am I doing wrong? Can anybody please help me?

Thanks in advance!

Hello,
Go to Finder-Preferences-General, and under the heading "show these items on desktop" make sure that the boxes for the External disks and CDs, DVDs, and iPods are checked. In fact, as long as you're there, feel free to check them all.
After you do this you should be able to see the volumes on your desktop which you can then eject allowing you to trash the dmg's.

Thank you so much for your help!

You're welcome.