I probably have missed something obvious. But, how do I fire missiles. I can get the heat seekers to lock on via target (t) and selecting the weapon (w), but don:t know how to fire. I am using a joystick (360) BTW. I guess I have to press something on the keyboard. But can't find the key. Any help or other pointers to stuff that I might have missed would be great. I am currently playing wc1 with the intention to progress through the whole series.

If "Enter" doesn't work then it's something with joystick. Did you read game's user's manual?

WC1, I assume?

It's in the reference card: you'll have to press 'button 1' and 'button 2' at the same time. What button 1 and 2 are depends on your joystick.
Button 1 fires the guns, at least, so you could try out all buttons on your stick while holding that one.