Is it possible, using some program or application, to lock Windows 7 so only a specific app can be used, for example Word, until a password is entered?
The use case you are describing is perfect for a White Listing application. In the past I have use Savant Protection and have had good success. Savant allows you to specify what applications are allowed to execute though either a configuration file or by "training" it. Savant will take all of the white listed applications, calculate their hash values and stoarge location and place all of this information into an encrypted database. Before an application is allowed to execute, savant compares the current state against the database.