Depending on what else your doing as part of the site definition I'd consider doing this using a web scoped feature and use feature stapling rather than creating a new site definition.
It would also be helpful if you could post the Modules element as well from the definition.
Anyway here's an xml snippet of provisioning files from a definition:
<Module Name="SampleForms" Path="Files\SampleForms" Url="SampleFormsLibrary">
<File Url="SampleForm1.xml" Type="GhostableInLibrary">
<Property Name="Title" Value="Sample Form 1" />
<Property Name="ContentType" Value="SampleForm" />
</File>
<File Url="SampleForm2.xml" Type="GhostableInLibrary">
<Property Name="Title" Value="Sample Form 2" />
<Property Name="ContentType" Value="SampleForm" />
</File>
</Module>
So in the above example the directory structure of the definition would be:
MyDefintion
Files
SampleForms
SampleForm1.xml
SampleForm2.xml
XML
onet.xml
...
Make sure the Lists element that creates the destination library is above the Modules element within the Configuration section of your onet.xml.