The film Kung Pow! Enter the Fist is indeed available on the (often uploaded by users under Fair Use / public domain claims, though the film itself is copyrighted by Fox).
Searching for "Kung Pow Enter the Fist Internet Archive" yields more than just the main feature. Here’s a breakdown of the treasures awaiting you: kung pow enter the fist internet archive
As the table shows, the Internet Archive is currently the most reliable source for watching Kung Pow in acceptable quality without paying scalper prices for a used DVD. The film Kung Pow