Error Help: Could not load file or assembly 'DocumentFormat.OpenXml' or one of its de

Full Error: Could not load file or assembly 'DocumentFormat.OpenXml' or one of its dependencies. There is not enough space on the disk. (Exception from HRESULT: 0x80070070)

Drive has 30 GB Free.

The file exists in the same directory where the Windows Service is running.

Thanks.