Nestopia is a Nintendo NES emulator for Windows XP. Nestopia is by far the most compatible of any NES emulator for Windows XP. Using cycle-exact emulation, it is able to run titles that rely on precise timing, and which therefore break under other emulators. It supports five extra sound chips and an astonishing 143 mappers.
Nestopia was initially developed for Windows by Martin Freij. The original sources may be downloaded from the Nestopia home page. The toolkit used to develop the Macintosh port, including the bridge code to link it to Nestopia, will be available in the longer term from my developer pages. Certain portions are available now, and more will be added in the future. This is one of the best versions yet.