How to release PageLayoutControl from memory

Hello,

I have an Engine application for Arcgis Desktop in vb.net. A PageLayoutControl included in a Windows Form opens an existing .mxd file.

When the Windows Form is closed, its contents are not released from memory properly until ArcGIS Desktop is closed.

Someone knows why this happens???

How to release memory when closing the Windows Form? How to code the finalize method???

Thanks in advance!!!

Mar