You need an alternative USB driver: Available for Windows 2000, Windows XP 32 Bit, Windows Vista 32/64 Bit, Windows 7 32/64 Bit 1. Extract archive. 2. Connect camera via USB and turn on 3. Search in extracted archive in subdirectory for inf_wizard.exe and run this file 4. Select in the second window 'Device Selection' your camera. 5. The driver will be provided and installed. 6. No PC reboot is needed. CHDK must support the PTP version 2.0 or higher(CHDK rev. 1155 or CHDK-DE rev. 646). For certain features to work properly, you may need to turn off review and flash of the camera.