As you use your computer, things happen, and not good things. Files begin to get corrupted, icons disappear etc. There is no way to prevent such happenings except to use the computer as a paper weight and none of us in this forum wants that.
To correct problems, if possible, it is suggested that at least once a week, you turn off your computer. When it boots up it corrects many of the defects that were created during the previous week.
Finally, with 7 we have an important safety valve. Shortly after installation and programs are installed and you are activated, take a system image, put it away. When you make changes to your programs etc, just write it down. When you have a problem like missing icons or worse, that cannot be corrected. Go to the system image, install it and make the changes that you wrote down. Important, do not make an image of the newly created download, it is not as pure as the one you saved originally. Listen to me and you will always have a perfect or nearly perfect OS.
Finally, enjoy Windows 7, because I know I am. Good luck