As of my last update in January 2022, "How to Lose a Guy in 10 Days" is available for streaming on the following platforms:
1. **Amazon Prime Video:** You can rent or purchase "How to Lose a Guy in 10 Days" to stream it on Amazon Prime Video.
2. **iTunes:** You can rent or purchase the movie through the iTunes Store and watch it on your Apple devices.
3. **Google Play Movies & TV:** Similar to iTunes, you can rent or buy the movie from Google Play Movies & TV and watch it on various devices.
4. **Vudu:** You can rent or buy "How to Lose a Guy in 10 Days" on Vudu and stream it on supported devices.
5. **YouTube Movies:** You can rent or buy the movie on YouTube Movies and watch it on various devices.
Additionally, the movie may also be available for streaming on other platforms or through cable/satellite providers' on-demand services. Check your preferred streaming service or provider for availability in your region.