Android 2.1 - MyTouch 3G Slide - Preparing SD Card mal-function - Formatted SD Card after taking out and putting back in :( Operating System: Android 2.2
Device: HTC MyTouch 3G Slide 
SD Card: Micro SD 8GB Sandisk card that is less than 1 year old 

Background: 
This feature formatted my working SD Card w/ all my pictures on it after i took it out and put it back into the same phone. I didn't add or delete any data from the device when i took it out... I checked the sd card on the computer and it only had 2mb of cache files on it while before it had 6gb of music and photos. I already tried mounting and unmounting the card. That doesn't help. The phone has recently been factory restored. 

Questions: 
1) Why is Android / MyTouch3G Slide formatting my sd card? 

2) How do I know if it's an sd card problem or a phone problem? 

3) How do I get the card to work w/ the pictures and mp3s on there? 

I'm thinking maybe I should prepare the card for android somehow- with a sd card formatter 

Update:  I recovered the files w Easeus Data Recovery, put them back on the card, and it formatted the files again. I'm thinking I should format my card for android 2.2 or mytouch3g so it accepts the pictures or put the card in while the phone is off to prevent this from happening again?
Android has to mount your SD card; that's all that "Preparing SD Card" does.  If that doesn't happen, then the device can't use the SD card.  Hopefully the format was just a fluke.  You should put test files on it (unimportant / already backed up) and see if it happens again.