it just simple... i think yours under Gingerfroyo Custom rom...
your defy got 4 way boot option? u can try press power button for 2 seconds then choose reboot and see got any option after that or it just reboot... if got other option like normal, hotboot, recovery, bootloader, you can choose recovery to start flash to other rom.
steps to flash to another rom:
*** please backup all important data like contacts, sms etc
1- download rom eg: WIUI 2.5.27 + RTLfix +FasterRock and put inside SDcard *U can create new folder eg: android rom and put there.

2- reboot into recovery with method above or you can enter recovery manually. 
>reboot and press volume down when Blue LED lid to enter bootloader> recovery > stable recovery
* to navigate inside recovery: vol up/down = up/down , power button/menu  = OK/Enter , Back = back

3- create backup of your current rom (optional) >backup and restore > backup all.

4- wipe data/factory reset then wipe cache partition

5- install zip from sdcard>choose zip from sd card and locate the rom eg inside Android Rom and choose yes. wait till it done

6- repeat #5 but this time locate RTLfix > yes after done repeat #5 and locate fasterRock >yes

7- go back to recovery main page, repeat #4 again

8- advanced > wipe dalvik

9- reboot.
* for first boot, it will take long time to enter main screen (2-4 minutes)