Even if entering a mathematical formula on a computer without stylus can quickly turn out to be a calvary, Windows 7 incorporates a tool to make it easier for you: I named the Mathematical Input Panel.
To access the Mathematical input panel, open the start Menu, click on All programs, Accessories, then Mathematical input panel.
The window consists mainly of a grid, where you will be able to enter your formulas.
To do this, nothing simpler, you just need to trace your equations by holding the left-click down. And automatically, Windows will recognise the different symbols drawn.
To make a correction, hold down the right-click while selecting the area to be corrected. When you release, a list of proposals appears: all you have to do is make your choice.
All you have to do is integrate your formula into a Word document, for example.