There are plenty of window controls to move and resize in Windows, and Win7 added a few new ones.
What you are probably doing is inadvertently performing some resizing actions and no one has told you what they are. Of course there is plenty of Help built into Windows too, just press the F1 key. But maybe you don't want to read either.
If all you really want to do is "see what's under your opened windows" then all you've got to do is place your cursor in the small gray box just to the immediate right of the taskbar clock. Doing that will make all your opened windows become see-through. (The edges will still be seen.) If you click on that gray box all the windows will go minimized. Another click of that same box will revert your windows back.
Here are a few more tips:
You probably already know about the maximize control button on the top right corner. But there are others as well.
If you grab the top header of the any window and "bang" (that is to move the cursor to the screen edge) anywhere along the top, then that window will maximize (go to full screen).
To un-maximize it just drag that same window header down just a bit.
Or, again to maximize the window just double-click the header. And you can do that again to un-maximize it, as well.
If you grab either the top or bottom edge of a window, and drag it to the respective top or bottom of the screen, then that window will go to maximum height, where the width does not change. Even when the height maximized you can drag that windows top or bottom edge to get the other side back in place.
If you grab a header bar and "bang" it to the left or right side of the screen edge then that will will be maximized to half of the screen, the half of the screen that you banged. To revert it back to whatever size it was, before becoming half-max, just grab the header away from that side just a little bit.
That half-max feature is really handy when you want to compare the contents of two windows. Just place one on the right, and the other on the left.
By the way you can also half-max the active window (the top most window, the one that has your attention) by just holding down the "flag" (I call it that, you might call it the Windows key) and press either the left or right arrow key, to get that window half-max to that side. If you've got the wrong side just (while still holding down the "flag") press the other arrow twice. You will see that window go through the middle size and then get to half-max on the other side with that 2nd press.
And here is a real hidden gem. If you have a lot of opened windows and you'd like all of them minimized except for just one, just grab the header of that one and shake it back and forth a few shakes.
There are plenty of other windows controls, and all you have to do is read a bit of the built-in Help (press F1).