If you have the OGR_FDW we discussed in OGR FDW Windows first taste built with ODBC support,
then you can access most any ODBC datasource from PostgreSQL. This is especially useful for Windows users. Two of the data sources I've been experimenting with are SQL Server
and MS Access. In this article, I'll demonstrate how to connect to MS Access with PostgreSQL running on a windows box. I think there is an Access driver for Unix/Linux most robust utilizes java. I won't go there.
Registry hack should no longer be needed for PostGIS 2.2 ogr_fdw bundle and up since these come packaged with newer GDAL libraries that have the fix.