I was following this tutorial about creating trees. Halfway through it he asked me to go to the Scripts window, press on add, then Wizards and then on "Twigs from Curves".. I don't have it. Infact i dont have anything.. All the scrips are missing.. How do i get them?? Thank you :)

It would be nice to know what particular tutorial you are following.

I googled some tutorials on the net and found particular script that I think you are asking.
Big buck bunny dev blog

Quote:

This is the python script - Tree from curves, its in Blender SVN development repository so any recent build of blender will include it (Script Window > Wizards > Tree from Curves)

I found the script and my blender version is 2.49b

Yep i re-installed Python and Blender and got the scripts, thanks :)

The tutorial was http://www.blenderguru.com/how-to-create-stunning-trees/

And by the way, say i want to add a new script.... how do i do that? I downloaded one and opened the file with Blender. I then clicked Alt-P to activate it.. But it only works for that opened file. If i open a new file (Ctrl+x) that particular script won't be there...

Just place the script into you script directory and blender will detect it when it starts up.
On windows the directory is:
C:\Documents and Settings\USERNAME\Application Data\Blender Foundation\Blender\.blender\scripts
or for Vista:
C:\Users\USERNAME\AppData\Roaming\Blender Foundation\Blender\.blender\scripts
where USERNAME is... well... ;)

Under linux the directory is:
~/.blender/scripts

Thanks :)