The menus are not located at the top of each window. There is a single menu at the top of the screen which changes depending on what program you are currently using. You can tell what program you are in because its frontmost window will be active (colored buttons as shown here) and the name of the program will appear next to the apple.
This menu headed by the program name is called the application menu, and has program-related tasks, such as Quit and Preferences (which is like Properties in Windows).
Although the Mac can run a two (or six, or ten) button mouse, the mice we've got have a single button (by the time you read this, we may have new ones with multiple buttons). On a one-button mouse, you can get the little mouse menu by holding down the [Control] key and clicking the mouse. On a multi-button mouse, you generally right-click just like on Windows.
If you wish to print to some printer other than the default choice (usually the lab's black & white laser printer), then you have to choose it from the printer menu that comes up after choosing Print from the File menu.
Instead of a start menu and taskbar, the Mac has a "dock", which shows all the currently running programs as well as commonly-used other programs I've selected. It can also contain quick links to printers, files and folders, and the trash. You are free to alter the dock, but your changes will be gone after you log out of that computer.
Finder is the program in which you navigate around the computer and move/copy files, run programs, etc. A finder window shows you files and folders, just like in Windows. You have a choice of views, just like in Windows. The Mac gives you a view not found in Windows, though: column view. In this view, you see the current folder and can scroll to the left to move up the hierarchy towards the "top" of the drive.
The finder windows also have a sidebar, which is a set of quick links to commonly-accessed folders on the hard drive.
If you need a Finder window, click the Finder icon in the Dock (the bluish happy face-thing) , and you will get a new Finder window.
Most common programs (Word, Excel, Photoshop, Illustrator) have icons in the dock. Common geology programs (Coulomb, Shape, Perplex, Thermocalc, Melts) can be found by clicking the "Geo" folder icon in the dock, and then navigating in the finder window that appears. If there is some other program or file you need to locate, click the magnifying glass at the top-right off the screen, and type the name (or part of the name) in the field that appears. You can then click on any of the results to open it.
As in Windows, each file has a program it is associated with, and which will run when you double-click it. You can open the file in some other program by any of the following: