Sony notebook motherboard schematic for MBX-237, version 0.30 according to the v030 tag, in a 2.68 MB PDF. Sony identifies its laptop mainboards by MBX numbers printed on the PCB, and the same retail model may use different boards, so check that marking first. The document is used to trace power and signal paths, locate components on a dead rail, follow the power-on sequence and verify expected voltages. Early-numbered versions can differ from production boards, so compare parts against the physical PCB.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @alischematics. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.