If you are looking for an onscreen keyboard for Windows 7, you should know that Windows 7 does includes plenty of useful tools. One of them is in fact an onscreen keyboard.
The built-in onscreen keyboard can be found here:
Start / All Programs / Accessories / Ease of Access / Onscreen Keyboard
Onscreen keyboard for learning 10 finger typing
The built-in Windows 7 onscreen keyboard might come in handy to control your PC when your keyboard is currently not working. However, if you are looking for an onscreen keyboard that only displays the keys that you type in onscreen then you might want to use the following AutoHotkey script.
Autohotkey is a nice tool that includes many scripts and allows you to map commands to any of your keyboard keys. You can get Autohotkey here and download the onscreen keyboard script here (right-click / save as)