Intel® Desktop Board DG35EC Technical Product Specification
Since "D33025" is common to dozens of boards, look for a small barcode label or white silkscreened text on the motherboard itself for these identifiers: Intel D33025 Motherboard Manual
Core Technical Specifications (Common for D33025-marked Boards) Intel D33025 Motherboard Manual
Specialized hardware databases like cpu-world.com or thecollectionbook.info often have documentation sections for Intel motherboards. Intel D33025 Motherboard Manual