Windows 7 has a built in sticky notes application in it, You can use it to write short to do notes or any other thing, that needs your attention as often as you visit your desktop.
You can access the, sticky notes application by clicking the start button, and search for Sticky Notes. Sticky notes will be shown in the start menu. Click it to pin a sticky note, to your desktop. You can add more sticky notes, by clicking the + button provided at the top left or close some by clicking the X mark in top right.
You can change the color of the sticky notes, by right clicking on the notes and by choosing a color from there. Sticky Notes can be useful in organizing your day to day work and making it systematic, so that you can do things easily.