There are in fact two virtual keyboards:
- the old accessibility keyboard (osk.exe) mentioned by @arnelgp
- the newer tablet keyboard (tabtip.exe)
You can use either but I'd recommend using the latter
If you want a demo of each keyboard, see my example app
This article discusses how to design Access apps for use on a tablet PC. It includes an example app with two different on-screen keyboards for testing purposes.
isladogs.co.uk