Created a second OS X partition, erased the first, now can't delete old partition I bought a secondhand macbook pro (early 2011). It was running Yosemite, but I wanted to do a fresh install, as initially I didn't have the password.

I created a 2nd partition and installed a clean Yosemite on to it. I then wished to use that partition, so I "erased" the original partition in Disk Utility, so that it would let me erase it. 
Once I did that, the "-" button was selectable, but it will not actually delete the original partition, or modify the 2nd one at all.

I believe part of this is due to the the fact that the startup disc partition is on bottom and not on top, therefore I wouldn't be able to drag the partition to expand it to the max capacity of my computer. 

That's all i'm trying to do. I realize that what I did was actually the long way (and pointless) to the results i'm trying to get. But how can I do this? I'm not worried about losing any info, as to me this comp is brand new. However, I don't have a USB stick with more than 8g, so I can't create a bootable disc for Yosemite, and pretty much need to install from app store download.
If the machine still boots, go to the App store and "purchase" Yosemite (its free).  Now boot the machine holding COMMAND R and boot to internet recovery.  If you see a poorly animated spinning globe instead of an Apple logo then you are on the right track.  Now you have can reformat the whole drive and do a clean install of Yosemite.