[Motorola Droid 3] LaZiODROID:
Ahhhh ok.

It sounds like you are trying to install zips via the stock recovery. That recovery will only install signed/official ones, not custom rom zips.

If you want to install custom roms, try this method (but I recommend browsing through the other threads. There is a lot of useful info out there). This is the safestrap method. Safestrap allows you to have your stock rom (that you are on now) in the "non-safe zone" and with safestrap you can enable the "safe zone" for installing your custom rom.

1) make sure your phone is rooted if it isn't already. There are threads about this... I used DoomLord's root (version 4) for my phone but read up.

2) install safestrap 1.08 (u can find it in the droid 3 development forum). It is an apk file.

3) when you run safestrap 1.08 from your app drawer, superuser will probably ask you if you want to allow it root access, say yes.

4) in the app, hit the first button. It will install safestrap so you can boot into safestrap recovery. When it says its done, restart phone.

5) upon restart, you will be greeted by the safestrap splashscreen. It gives u 10 seconds to hit Menu to take you into safestrap recovery. Otherwise it will just continue with booting.

6) so hit menu. Safestrap ecovery appears. It will indicate that safe mode is not enabled yet. You are in non-safe right now (your stock rom)

7) this step is optional but I'm sure everyone will recommend it (I do also). Navigate your selection with the down/up volume buttons and hit power when you get to "backup". This will back up your non-safe zone and dump it onto your sdcard (internal or external). You can restore it to your non-safe zone (only) if you happen to mess up your non-safe system. The backup will be stored in /safestrap/backup. of whatever card you select.

8) now that that's done, it will take you back to the main menu of safestrap recovery

9) Go to "safe boot menu" and hit Toggle safe zone. Don't do the quick toggle, just do the normal one (the first one)

10) when that is done, you will notice the colour of the text has changed. And at the top it will say safe zone enabled. You can now install your custom rom by going to "install zip from sdcard" from the main menu of safestrap*

*Note that when installing roms, make sure to choose Wipe Data first. It will wipe your data and cache. Then go into mounts and storage and choose "format /system" (thanks Endo). Some people also like to go into the advanced menu and wipe the dalvik cache as well (is this necessary? I do it every time because I had to back on my old htc... maybe someone can comment on this?) It doesn't seem to hurt anything when I do it, so...

So after your wipes, you can go to "install rom from sdcard" . Choose the .zip of the rom (of course) to begin install. When the rom has finished installing, you can go back to the main menu and choose reboot phone. You will be greeted by the safestrap splashscreen again. It will tell you that safe zone is enabled. Wait the 10 seconds to boot normally or you can hit the search button to go immediately.

On first boot of many roms, it may take a little longer than normal to start up. Be patient. If it never boots (and you are looking at the boot animation forever... say more than 5-10 minutes?) Then... somethings wrong, or you may have forgotten to do your wipe procedure, but go to that rom's thread and read all the posts to see if others experienced the same thing... someone could have posted a good suggestion or solution

Oh, if you want to switch back to non-safe mode, restart phone, get into safestrap recovery, go into safe boot menu, and hit toggle. Then restart phone.

If something disastrous occurs, there are Unbrick and Fastboot threads in this forum where you can download a stock rom for your phone and flash to your phone via RSD Lite, which will pretty much restore your phone to stock. (No more safestrap, no more root). Read through those to get more info.

Hope this is helpful. Good luck!

Sent from my XT860