Boardview archive of 1.01 MB whose name mentions only P51, MB, NPB and version B. No brand is given, so the platform cannot be identified from the name alone, and version B probably refers to the board revision. Before using it, compare the codes and revision silkscreened on your mainboard with the file's contents. Once confirmed, open it in a viewer such as FlexBV or OpenBoardView to locate parts, follow power rails and signals, and choose measurement points.
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 @BoardSchematic. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.
7-ZipWinRARThe Unarchiver (macOS)