Migration assistant stopped working and has left me with 100gb in 'other'? How do I delete 'other' and what is it exactly?

Question

I recently invested $2000 (one week ago) in a Macbook Pro Retina 2014 2.8ghz 512gb. Dont get me wrong, I am in love with my product and am extremely satisfied but I have honestly encountered nothing but issues.
My first issue was the transferring of data from my 2010 white macbook 500gb. Both laptops have Yosemite installed and are 100% up to date but I have spent the last week getting them to talk to each other. I am not new to the workings of Apple but I have never endeavoured to use applications such as airdrop, migration assisstant or even bluetooth.
My first attempt was to transfer 200gb of files (Photos mainly, I'm a photographer) to my other laptop via a 64gb USB in segments. But after an hour and only 10gb getting copied across, I decided other alternatives may be of more help.
That is when I came to my first dilemma: AIRDROP. Airdrop is crazy. Yes I did click the option on my retina to search for older macs and yes they did connect. I can send files from my MBR to my white macbook 2010 immediately but my old macbook will not send files to my retina. Yes all of the necessary sharing settings are in place - both MacBooks have the same settings selected so I cannot figure out what to do. Information on this subject would also be helpful yet it is not the end of my troubles.
Second Issue: Migration Assistant.
So yesterday I discovered this little 'gem'. I am a very impatient person so you can imagine i did not appreciate 20 hours of file transfers (via wifi as i do not have a thunderbolt to ethernet adaptor for MBR). Anyway that's all well and good if it actually worked. But of course it did not. I followed apples instructions and I was down to my final 4 hours this morning when my MBR told me the connection was lost and to reconnect. It was making the loudest whirring noise like air coming from inside the hard drive or something. I freaked out. My $2000 machine should not be doing this. It was only a little bit warm; not hot but it was incredibly loud, I'm not sure how to describe it. Keep in mind this computer is brand new so please tell me: WHAT WAS THE SOUND?!?!?!?! AND WHY? what was wrong? what could I have possibly done wrong? My wifi WAS working because my desktop PC was connected. So i waited and waited. Of course I couldn't actually do anything without quitting airdrop and in the end that's just what I had to do. A lot of time wasted for such an unsuccessful cause.
That brings me to my final issue:
So after migration had.... "completed" or crashed or whatever you want to call it, I at least assumed some of the files had maybe copied over and i could just resume from where I left off last time somehow. Oh how stupid that assumption was. My user account did in fact copy over but not a single file copied. And yes, I did log into that user account to check. ANYWAY, I went onto "about this mac" to see my storage info (still being optimistic about my wasted 20 hours). SURPRISE SURPRISE: Yet another problem. I now have 100gb in "other". This macbook is brand new. I should not have any GB in other. I am so incredibly annoyed. HOW DO I DELETE OTHER?! (preferably without downloading software) and is there anything else of importance in other that i should be careful not to delete that is contained within other?
I am only 15 years old  and this was a massive investment for me so I treat my Macbook like a baby. And no, I'm not spoilt by my parents. I had to work at Subway for a year to earn $2000 - without spending a single cent (My wage is only $9.00AUD an hour so i essentially worked some 222 hours for this macbook). And I'm not crazy, I needed it for school.
Anyway I'm not impressed with apple. I have Applecare but they aren't open on the weekends or whenever I try to call so that hasn't exactly been helpful. PLEASE HELP ME.

Answer 1

Make a note of all your settings for Wi-Fi in the Network preference pane, then delete the connection from the connection list.
Launch the Keychain Access application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Keychain Access in the page that opens.
In the keychain list, an item named "System" should be listed. If it isn't, select File ▹ Add Keychain from the menu bar and add the following:
/Library/Keychains/System.keychain
Now search in Keychain Access for the name of the wireless network (not the name of the router.) Double-click one of the items and check the box labeled Show password in the inspector window. You'll be prompted for your keychain password to confirm. Make a note of the network password. Then delete every "AirPort Network Password" in the search results. Quit Keychain Access.
Go back to the Network preference pane and recreate the Wi-Fi connection with the same settings as before. You do this by clicking the plus-sign icon below the connection list, and selecting Wi-Fi as the interface in the sheet that opens. Select Join other network from the Network Name menu, then select your network. Enter the password when prompted and save it in the keychain.