Hey Deltahero! What type of mac is it? Did you get it new? The reason I ask is that your issues don't correspond to the mac being setup for system defaults.
The track pad zooming issue. Click on the apple in the top left of the screen, open system preferences. Select trackpad. This screen will allow you to customize your track pad behaviour.
As for the not being able to edit your files after you save them, that sounds like a permissions issue. Select the file, control click (right click), get info. Or select the file, and hit open apple-->I. At the bottom you will see what permissions you have. To edit them, click the Lock icon, type in your password, and then change the permissions beside your login name to read & write.
View full screen in your browser or video? There is a button the top left or right of a window/browser that is a + sign. Click that to fill the screen with the window. In a video player, this optino is typically under the "view" menu at the top.
You may want to repair your permissions as well. Go to applications-->utilities-->disk utility. Select your main drive, and run the verify disk permissions followed by the repair disk permissions. You could just run repair disk permissions, but I like to be thorough.
What file format are the attachments you are trying to view?