Try the lower glove box. It is recommended to replaced the cabin air filter every 2 years or 30,000 Miles. Here are some instructions with pictures;
http://john1701a.com/prius/documents/Prius_Maintenance_Air-Conditioner-Filter.pdf
RepairPal Certified shops can diagnose and repair your 2005 Toyota Prius. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
Thanks Man! you rock -