Like emgee says, you probably don't have to worry about it right now.
If you're just dealing with documents and such for the most part, you're not going to fill up 250GB more data very quickly.
And you already have an external drive, which I assume you use to backup critical files, so you don't need more disks just for backup and security.
However, there are a couple things that need to be addressed:
First, megabytes and Gigabytes are measured not in strict mathematical sense of Giga equalling 1000 Mega's, they are really based on a factor of 1024, which has to do with how computers count more than anything else. The numbers that harddirve makers use will vary depending on how they want the drive to look, some will be based on a 1000 factor, and others on 1024 factor, and you'll see both on the same package sometimes with no label to show you which is which. Because of this it really isn't important, except in an abstract sense, to try and match of 196GB with 196,000MB. It's useful to get a ballpark figure, but not if you're looking for accuracy.
Second, virtual disks have nothing to do with increasing the amount of storage on your computer. Think of a .zip file: it is a file that contains other files. A virtual disk is just that except with a different purpose. A virtual disk is a file that contains other files, specifically for the purpose of pretending to be a hard drive for a virtual computer, which is a computer that only exists in software running on a computer. Virtual disks and Virtual computers are used for testing, application development, "sandboxing", and in some cases saving power and resources by allowing a single physical computer to act like several different computers.
Finally, being more familiar with software than hardware is perfectly OK. Most of the world gets by just fine being much more familiar with software then they are with hardware. Computer makers know this and hard drives and storage options are becoming increasingly easy to apply and use by software people, such as yourself.
Even if you start working with and making significantly more data than you are now and find you are running out of space, you can get huge external hard drives nowadays for relatively low prices. And just like your current external hard drive, you just plug it into your computer and begin enjoying tons more space easy as that.