I googled it and couldn't find anything really other than the 'redownload El Capitan' which I am very impatient, so I decided to ignore the error, reformat my USB stick again and run Unibeast. About five minutes later it threw an error at me. So I quit Unibeast out of frustration and ran it again. I left the cursor on the end of the progress bar and came back 25 minutes later and the cursor had shown that the progress bar had not moved and there was no activity on the USBs end either.

I seen that Virtualbox was showing no activity from the USB stick. It said 'copying files' but the bar seemed to be in the same spot as when I left. The first time I did this, I waited at least a little bit before an hour (about 50 minutes) and checked on the progress. I downloaded El Capitan through the app store and formated my 32GB flash drive and am now currently installing it through Unibeast.

I have Mountain Lion currently running perfectly fine on Virtualbox. I am on Windows 10 and I'm wanting to dual-boot Mac OS X with it.

Unibeast install os x el capitan