Get Hard Drive Volume Serial

public string GetVolumeSerial()
{
uint serNum = 0;
uint maxCompLen = 0;
StringBuilder VolLabel = new StringBuilder(256); // Label
UInt32 VolFlags = new UInt32();
StringBuilder FSName = new StringBuilder(256); // File System Name
string strDriveLetter = "C:\\"; // fix up the passed-in drive letter for the API call
long Ret = GetVolumeInformation(strDriveLetter, VolLabel, (UInt32)VolLabel.Capacity, ref serNum, ref maxCompLen, ref VolFlags, FSName, (UInt32)FSName.Capacity);
return Convert.ToString(serNum);
}