The Android OS has a certification feature that prevents you from installing unauthorized applications on it. However, XDA member fluffyarmada found a workaround to avoid the certification procedure, which allows you to install any non-market application directly from your SD-Card. Unfortunately, the workaround is pretty difficult, and you will need to have some serious Android skills in order to be able to do it. Your device needs to be rooted to get this working.
Originally posted by fluffyarmada
If you update the “/data/data/com.android.providers.settings/databases/settings.db” file so that “install_non_market_apps” = 1 instead of 0, you will be able to install non-market apps off of your sdcard or wherever.
This works for me at least, but you’ll have to root first.
You can find more information in the hack thread found in the Aria forums. Make sure to search the forums first before asking questions.
Edit: This workaround is only needed for the HTC Aria. All other Android devices let you do this via the settings -> applications menu. Thanks for the replies!___________________