Yes. In Office Visio 2007, you can open and use any Visio
diagram created with a previous version of Visio.
You can also open an Office Visio 2007 diagram in Visio 2003
because they both use the same file format.
You can open an Office Visio 2007 diagram in Visio 2002 by first
saving the diagram in the Visio 2002 file format. Be carefule
though, version-specific functionality will be unavailable after
saving your diagram in a previous version of Visio.