There been plenty of topics in the couple weeks that players are having problem that SA or SAMP doesnt start.
BEFORE creating a topic check these things:
1. Delete the gta-sa.set in GTA San Andreas User Files, located in My Documents.
2. Check if your San Andreas is version 1.0 or downgraded to it, SAMP wont work without 1.0 version.
3. If none of these worked, Re-install the game and downgrade if needed, and see if its works.
4. Make sure you dont have any mods, most of them will not work with SAMP or Argonath server.
5. If using Vista - Make sure you run it as administrator
Thank you for your time.