This is an option in Windows 7 and can be easily disabled.
Click Start or tap the Windows key and click Control Panel from the right-hand list. Once the Control Panel opens and populates, click Mouse.
In the Mouse Properties dialog click the Pointer Options tab and uncheck Hide pointer while typing. Click OK in the lower right.
As this is a Windows system issue and not specifically Office related, I will move this thread to Windows 7, Personalization and Ease of Access.