I was looking for the size in GB, so I just improved the code from Superman above with the following changes:
public double GetTotalHDDSize(string driveName)
{
foreach (DriveInfo drive in DriveInfo.GetDrives())
{
if (drive.IsReady && drive.Name == driveName)
{
return drive.TotalSize / (1024 * 1024 * 1024);
}
}
return -1;
}