To get the POV-Ray v3.1e executable for MS-Dos -

  o download povmsdos.exe.
  o run it in a temporary directory.
  o run the install.exe program produced.
  o follow the instructions.

To get the POV-Ray source code in C for MS-Dos -

  o get the executable and install as shown above
  o get povmsd_s.zip and unzip -d in your \povray3
    directory.
  o read compile.doc and other docs

Note: Source isn't necessary just to run the program.

If you already have POV-Ray for MS-DOS v3.1 or later
installed and just want to upgrade to 3.1e, you may
download povmsexe.exe, which is a self-extracting
archive containing the new binary only. Do NOT download
this if you don't already have POV 3.1! It is of no
use to you in that case.