If you need a high-quality computer algebra system (CAS) without paying, consider:

If your goal is to use Maple 18 or Maple 17 at no cost, here are legal alternatives:

If you're looking for high-quality educational content or tutorials on using Maple or similar software, consider:

If you're interested in using Maple 18 for educational or professional purposes, I recommend the following steps:

Be extremely careful. Running unknown executables can:

Always scan any suspicious file with multiple antivirus engines via VirusTotal before running — but the safest choice is to delete it.