In response to MattieuQ's reply;

Amend the update statements to the following

update #Files set [FileName] = substring (RawData, 40, 255) where FilePath is NULL

update #Files set FileSize = convert(decimal(18, 2), replace(substring (RawData, 22, 17), ',', '')) where FilePath is NULL and isnumeric(substring (RawData, 22, 17)) = 1

update #Files set DriveLetter = substring(FilePath, 1, 1) where FilePath is not NULL

update #Files set FileSizeInMB = CONVERT(decimal(18,2), FileSize) / 1024 / 1024,

FileSizeInGB = CONVERT(decimal(18,2), FileSize) / 1024 / 1024 / 1024

where isnumeric (FileSize) = 1