TLJ is my second favorite P&C adventure title ever. It's a close one, but first goes to MYST 4. I played the DVD version of TLJ and the only problem I had is that at one point you need to use the other .exe file to run it. Otherwise there's no problem.

There's a preferences.ini file where you can change the bool_StartFullscreen value from 1 to 0. That should do it.
EDIT, On the other hand it might not be as easy as that. I just checked and i can't get either gog's or steam versions to run in windowed mode by changing that value...I must be missing something fairly obvious here...
EDIT 2, Ok, i knew i was missing something.
The preferences.ini file that needs to be edited is not the one in the game folder
In Win7 the preferences.ini file that needs to be edited is in:
C:\users\<user>\AppData\Roaming\The Longest Journey.
I had to add this two lines to get windowed mode:
[DirectX]
bool_StartFullscreen=0
Windowed works.
I'm running the gog version on a 24'' LCD and it looks good though...

Sure you can. That's what a lot of us does.

While I understand that view, I personally leave Steam on all the time as it is not just a game launcher, but a community. I have friends from forums on there I can always shoot a quick message to, or ask to join a game... my best friend from high school is on there and I can see what games he is playing and give him a quick shout.
The only reason I would ever have AIM or something like that on my comp is to setup online games and do similar things, but with Steam you can use it instead and never have to bother with those other programs. It is fairly cool, for me anyway.
None of that really has to do with what I said though, which is basically that my preferred release on GOG is of the more "really old games that other sites ignore and cost a load of cash on ebay" variety. Rather than give $100 to a collector on ebay you can buy these old titles in working condition on GOG for $10 or less... games amazon and Steam consider too old to bother with. That was the reason GOG appealed to me...

DUCKYYYYYYYYYYYYYYYY!

Thanks Namur!!!
I'll pick it up tonight or tomorrow then, and give that a try.
Much appreciated. :)

No problem :)
I'm sure you'll have a great time with TLJ.

Thanks, I was wondering about this as well, as i like to be able to make use of my other screen while playing.

No problem mate ;)
This quick fix does have a slight incovenient if you want to drag the window from the upper left corner (to the center of the screen, for instance)
I didn't tried it myself, but here's another possible solution for that. (credit goes to Vestin)

I may not be eligible, but +1 rep point for your generosity, sir.

Well, if noone claims it, you might be eligible. Let's wait and see....and thanks!
OK, nobody took me up on that. Here;s a new one. If you have at least 70 rep, are fom Australia, and have a cat as your avatar, you have 5 minutes.
Man, Cat missed it. I'll try to give it away later.

Hahaha, I was on train at the time you posted that. :P

Maybe me?
Maybe?
I''m Aussie, and am of a lower rep
But Catshade is also Australian and an honourable person
I do not own this game, and do desire to play
But Catshade also desires it, and he/she is an honourable person (without being sexist)
I have a will, and luck is on my side
But Catshade too has won many a game, and he/she is an honourable person
Thus this speech doth end my story, the story of a man who loves free stuff
Prkaaspeare, Catshade Caesar
The story of a jealous man, prakaa, who desires the luck and power of Catshade
Sorry Cathsade, if we spirits do offend...
But think not of ths, blah, blah, blah
Thanks GOG :)

Cole is cool :).