Hard disk drives (HDD) serve as a major storage media on your computer. Hard drives are manufactured in a wide range of storage capacities, and more than one drive might be installed on your computer. Hence the free disk space highly depends upon the system configuration as well as the amount of data that is already stored on the hard drive(s). Windows Explorer in the Windows operating system or the Finder manager on Mac computers allow you to quickly access your hard drive information, including the amount of available disk space.
In Windows XP, Vista or 7
Log into your account in Windows XP, Vista or 7. Click the Windows "Start" button.
Click "Computer" to display disk icons representing hard drives.
Right-click on the hard drive icon. For example, you may be able to click on disk "C:" and choose "Properties" from the context menu.
Select the "General" tab and read the free space on the disk given in gigabytes (GB).
Repeat steps three and four to find out how much free space there is on the other hard drives on your computer if you have more than one hard drive.
Sum up the available space on all hard drives to figure out how much space is left on your computer. For example, if 25 GB are left on the "C" drive and 123 GB are free on the "D" drive then the total available space on the computer is 148 (25 + 123) GB.
In Mac OS X
Open a Finder window by clicking the "Finder" icon.
Select a hard drive icon in Finder. For example, you may select "Macintosh HD."
Press the key combination "Command" + "I" on the keyboard to open the "Info" window for the hard drive.
Click on a small triangle next to "General" in the Info window to expand that section.
Read the free space on the hard drive in the line "Available."
Repeat steps two through five to find out the free space on any other hard drives that might be on the computer.
Sum up the available space on all of the hard drives to figure out how much space is left on your computer.