I just ran this up on a Win7 box and it compares very favourably to some of the other apps I have seen plus this has some nice features, is free to download and register and gives access to some nice updates, you can even print off data cards
http://www.weatherbyrifler.com/index.php?ind=downloads
Yes, I know the site is in Norwegian!! Choose Ballistic Hunter and off you go, well worth a look.
Tip - you can swap between metric and imperial data inputs.
Full details can be found here (In English)
http://www.weatherby.dk/showthread.php? ... ew-Release