출처 : http://blog.naver.com/PostView.nhn?blogId=higil&logNo=14056226&widgetTypeCall=true
CString str;
float TotalBytes, fTotal, FreeBytes, fAvail, fUsed;
ULARGE_INTEGER uliUserFree, uliTotal, uliRealFree;
CString strDirectoryName="d:\\"; // 알고자하는 디스크이름
if(GetDiskFreeSpaceEx(strDirectoryName, &uliUserFree, &uliTotal, &uliRealFree))
{
TotalBytes =uliTotal.LowPart+(double)uliTotal.HighPart*(double)4294967296;
fTotal = (float)(TotalBytes/1024/1024/1024); // Convert (GB)
FreeBytes = uliRealFree.LowPart+(double)uliRealFree.HighPart*(double)4294967296;
fAvail = (float)(FreeBytes/1024/1024/1024); // Convert (GB)
fUsed = fTotal - fAvail;
str.Format("D:\ Total %.1fGB, Free %.1fGB, Used %.1fGB", fTotal, fAvail, fUsed);
MessageBox(str);
}