Question: What system used CP1251 encoding?
Sentence: Nevertheless, the spread of MS-DOS and OS/2 (IBM866), traditional Macintosh (ISO/IEC 8859-5) and Microsoft Windows (CP1251) created chaos and ended by establishing different encodings as de facto standards, with Windows-1251 becoming a de facto standard in Russian Internet and e-mail communication during the period of roughly 1995–2005.
Answer in sentence: yes