Have you read the installation instructions when downloading the sis package?
Have you checked that your device Firmware has been updated to latest version?
If yes to both, please proceed..
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Q: Can't install. My N8/C7/C6-01 tells me that application is already built in?
A: Your device firmware is old. Early versions of Symbian^3 system have a bug that prevents the installation. You need to have PR1.1 or newer firmware version. NOTE: by the time of writing the new version is not yet available everywhere.
Q: I get a system error note when starting aplication?
A: You have installed the application to memory card or mass memory. The application works only if installed on C: drive of S60 5.0 touch devices (N97/N97 mini/X6/5800/etc..).
Q: I get a warning "Application may not be compatible with your device" when installing?
A: You can ignore this error. Some releases versions of diagnostics can cause this message but it doesnt affect the application or your device.