You must first set your local flash player security settings to use your C:\ drive..
For PPT, you must set the security settings in Internet Explorer, NOT Chrome or Mozilla
Here is the link to access your security settings manager.
http://www.macromedia.com/support/documentation/en/flashplayer/help/settings_manager04.html
A PPT will not be able to reference a relative path to a CSV file. The reason is the active X controller inside of PPT does not always use the location of the PPT file as the host directory. The workaround we have used for this limitation is to use a macro located inside of the PPT that will make a copy of the CSV file on the C:\ drive. Then we configure the CSV Connector inside of the SWF to always load data from C:\.
UPDATE ON PDF:
PDF no longer supports loading local files (CSV or Shapefiles into dashboards when embedded in PDF. Adobe has sandboxed Flash Player inside of a PDF from accessing your local file system even with flash player security settings enabled on your machine or embedding files inside of the PDF.