While the trend is too have no software on a personal computer (e.g. Chromebook) many of us still prefer a real computer and that is how I ended up buying an Acer Aspire One netbook. At that time, I simply planned on buying an external CD-ROM drive to upload new software that I already own.
However, before I could get to that, and while setting up a network at home, I realized that other wireless devices in my house were all showing up in the network window of my computer. It was so easy to add the another computer with a CDROM drive to the network and enable sharing. Now that I could access all the drives on the other laptop, I enabled sharing on the CDROM drive too (right click on the drive icon, and then properties and sharing). And that means that I could use this drive as if it belonged to my netbook (I am sure this might be networking 101 to the pros but as an amateur this was an awesome discovery to me because I could not find the answer to this through a Google search). In no time, I was able to upload new software (insert the software CD and then from the computer on which you want to install the program, open the drive, find the .exe file and double click it), and obviously, I can share all files and folders as well.
If this sounds like rocket science, before you go and get an external drive (which are becoming obsolete anyway), try it out or ask for help from someone who knows a bit about computers.