In the age of inexpensive 2 terabyte hard drives, a few gigs might not matter, but there are situations where you might need that extra space.
For instance, if you purchase a solid-state drive to contain your operating system, applications and games, you'll grow to cherish every salvageable gigabyte. There a few simple adjustments you can make within Windows to regain some drive space.
For starters, you can disable hibernation. Hibernation basically writes your current system state to a non-volatile memory source, such as your primary HDD or SSD, allowing you to turn off your system and restore your progress at a later date. To save a little more space, you could also reduce the size (or entirely disable) system restore. Granted, it's better to be safe than sorry, but there are better backup solutions out there.