You can watch "How to Lose a Guy in 10 Days" on several platforms:

• Netflix (subscription required) offers the movie for streaming, allowing offline downloads as well

• Disney+ also streams the movie as part of its catalog

• Pluto TV streams it for free with ads

• You can rent or buy it digitally on platforms like Amazon Video, Apple TV, Microsoft Store, Google Play, Fandango At Home, and YouTube

So depending on your preference, you can either stream it with a subscription on Netflix or Disney+, watch it free with ads on Pluto TV, or rent/buy it digitally on various stores.