android run Calculator报错

如题,我在eclipse下一次导入源码中的Calculator、Calendar、CameraOpen、DeskClock等工程,右键项目Run as - Android Application,能正常启动模拟器(2.3的),但是在控制台下显示报错,提示:
[2012-03-07 14:17:17 - DeskClock] HOME is up on device 'emulator-5554'
[2012-03-07 14:17:17 - DeskClock] Uploading DeskClock.apk onto device 'emulator-5554'
[2012-03-07 14:17:24 - DeskClock] Installing DeskClock.apk...
[2012-03-07 14:17:43 - DeskClock] Re-installation failed due to different application signatures.
[2012-03-07 14:17:43 - DeskClock] You must perform a full uninstall of the application. WARNING: This will remove the application data!
[2012-03-07 14:17:43 - DeskClock] Please execute 'adb uninstall com.android.deskclock' in a shell.
[2012-03-07 14:17:43 - DeskClock] Launch canceled!

尝试解决:根据错误提示,说是这个Calculator已经存在,需要删除?  于是我在dos下进入sdb目录下,一次执行如下命令:
adb remount -- remount succeeded
adb shell rm system/app/Calculator.apk -- rm failed for system/app/DeskClock.apk, Directory not empty
adb uninstall com.android.deskclock -- Failure

求解释,求答案...
问题补充
回复楼上的,你看清楚我写的是源码中的应用,不是SDK中的APIDemo,并且是模拟器系统自带的Camera、Calculator这些应用,你手动能删掉?
问题补充
回复楼上,我现在就是删不掉模拟器上的原生APK,你看我用root删依然删不掉,是什么原因呢?

rm掉data/data下Calculator的文件夹

那你就直接手动到模拟器去把那个程序卸载试试

这是因数模拟器的apk跟你现在的apk签名不一样。解决方法,把模拟器的apk删除掉。再把你的apk push 进去或者install

你可以把你的包名修改一下。就可以运行了。

[quote="su1216"]rm掉data/data下Calculator的文件夹[/quote]

adb root
adb remount
adb shell rm -r system/app/Calculator.apk
adb uninstall com.android.deskclock