Why dont you just use the one Windows has?
Start>All Programs>Accessories>Accessability>On Screen Keyboard
Make a shortcut to the desktop.
I use Instantsheller and it boots E-Touch as my main program to boot into.
I have an extra I-Pac that I attached to my setup that I put 3 buttons on the back. 1-Control 1-Alt 1-Delete ( I know, waste of an I-Pac and expensive buttons) Hit all three at once and the Windows Task Manager comes up. From there I just click New Task, at the prompt : explorer is already there because when I had a keyboard attached I typed it in, Then just hit OK then Explorer starts up, then I just click the Desktop and the on-screen keyboard shortcut is there.
Everything I need to do is on my Desktop so I put shortcuts there and just click them. The tiny keyboard is a little trying at times, but I have big fingers.
Hope this helps!

Fordman