If you are getting that while stressing your computer with a game, that is very good. 42c is nothing in the electronics world, depending on what processor you are running, it could go much higher. If you ever start to hit around 60-65c, then you should start to worry.
Just to put things in perspective, your video card is probably up in the 50's to low 60's (higher if it is overclocked). Don't take my word as absolute, however, since I have little experience with Nvidia cards, so I can't vouch for them.