The MSP image format is associated with one of the early versions of Microsoft Paint, Windows popular drawing tool. Files with the MSP extension can only contain monochrome images and they were created or edited using Windows ver. 2.0, released in the 1980s. In case you found such a file it is probably very old and opening it with your current version of Microsoft Paint or with another regular image viewer might not be possible.
JPEG JPG PNG GIF TIFF TIF BMP ICO EMF WMF AI PDF EPS PS EPI WEBP WEBPLL JP2 PCX TGA DWG DWF DXF DGN WMZ CGM DRW GBR PCT MIF PLT PCL SVG WPG CIN DCX DIS HRU MTV PRC RAD PIC RLA QRT SGI XBM XPM SWF CAL PSD JXR BPG APNG DDS SVGZ CG4 FLIF