You could set up a network and transfer it that way (The time will depend on your internet connection speed) so probably not the best route to go and could take about 50 hours where you would not be able to use your internet at full speed.
The best way is to use an External Hard Drive (It is simply a regular mechanical hard drive encased). This will allow you to transfer the 100gb files in an average of 7 hours (depending on the type of harddrive, 5400rpm/7200rpm, etc)
I would strongly suggest that you invest in one to backup all your files, you never know when your computer might crash, lose files, etc.
http://www.amazon.com/Seagate-FreeAgent-Ultra-Portable-External-STAA1000101/dp/B0045JLPMO
This is a 1tb seagate External Hard Drive
both Seagate and Western Digital (Hard Drive Manufacturers) have sales every week.
You should look for a 1 tb External for $59ish. Don't overpay!
I suggest Slickdeals.com - check it daily and you will find one this week
I forgot to mention, if moving 100gb of files is something that you do like once a month/year then a USB 2.0 hard drive will save you some money.
But if you're like some people who transfer huge files everyday (5/15gb multiple of files each day) then go with a USB 3.0 (It's much faster but also slightly more expensive, like $10-$20 more)