Use TweakWindow or Nailit.
An absolutely safe program is "TweakWindow". It was created a long time ago, so it will work on Vista only in a certain way. If safety is important to you, however, use this program.
Download it from
Install it in the usual way.
The only problem is the buttons will not appear on the menu bar of the program on top, as "TweakWindow" intends. It does still work within the program, however: if you place the curser on the menu bar (actually the area right at the top of the screen) of notepad or another program on top, then right click. You can choose what you want to do from the list that appears. You will probably find that the "tweak Window" menu appears at the top of programs after the computer is rebooted a few times.
When it is installed you will have an icon on the desk top. Click this icon.
Internet Explorer or Firefox will already be running. Open Notepad. Now hold down "Alt", press and hold "F1", click and hold "curser" on Notepad, release "F1" then "Alt". Click the curser anywhere again. You will see that "Notepad" is on top and you can see through it. If you want to see a solid "Notepad" right click on the "TweakWindow". Choose "Options". Then untick "Make window transparent when it stays always on top"
This program is like Tweakwindow and it many ways it is simpler. Just download the Nailit exe file. Create a new folder in "Program Files". Put the Nailit.exe file into the folder. Right click and drag the file onto Desktop and make a new shortcut.
To stop the keep-on-top function of both programs working just close the "switched on" browser and re-open it.
Note: You can have more than one program on top.