iphone 3gs don't boot after jailbreak / itunes finds the phone starts backing up

[Meric]

I wanted to jailbreak my friend's iphone 3gs by jailbreakme.com

after jailbreak, I installed 1 app and it didn't restart the springboard..I did hard reset and its not booting now....

I see the apple logo.. that loader icon is turning then stops...

at this moment itunes recognizes the phone and starts backing up.. but around 30-40 % on the status bar.. the phone reboots again...

is there anyway I can back up the phone?

I read about the DFU mode but my friend doesn't wanna lose the contacts and photos in the phone..

she didn't have any backups...

does DFU firmware reinstall deletes the data ?

thanks!