Even though it seems that Grabtxt isn`t exactly a screen capturer, what it does is capture the text in the typical dialogue boxes that open in Windows (which are impossible to copy and paste using traditional methods).
This way Grabtxt will be really useful when an error message appears, or other information. Thanks to Grabtxt you can copy them and search for information about them on the Internet.
For Grabtxt to work correctly you need to previously install .NET Framework 2.0 or later.