TraineeWindows 10/NVidia apparently no longer supports DXT1 of S3 Texture Compression (S3TC) (sometimes also called DXTn or DXTC) is a group of related lossy texture compression algorithms originally developed by S3 Graphics, Ltd. There is a license fee for their use. Windows 7 and Pre 1511 Update Windows 10 along with GeForce drivers did support this compression.
NVidia is blaming Microsoft and Microsoft is blaming NVidia so it is unlikely to be a fix anytime soon or at all.
DXT1 (also known as Block Compression 1 or BC1) is the smallest variation of S3TC, storing 16 input pixels in 64 bits of output, consisting of two 16-bit RGB 5:6:5 color values c_{0} and c_{1}, and a 4x4 two bit lookup table. The lookup table is then consulted to determine the color value for each pixel, with a value of 0 corresponding to c_{0} and a value of 3 corresponding to c_{3}. DXT1 does not store alpha data enabling higher compression ratios.
Some Details @ http://www.fsdeveloper.com/wiki/index.php?title=DXT_compression_explained
and https://forums.geforce.com/default/topic/903189/geforce-drivers/geforce-358-91-amp-359-06-win10-64bit-drivers-make-some-bmp-files-unreadable-/post/4755289/#4755289
