Default [Q] Custom rom on chinese tablet

Hi,
I have a Vimicro fj_vortex and I wanted to know if and how I can flash a custom rom on it,anyone can help me?
I can't even enter recovery mode or fastboot using
Code:
adb reboot bootloader
Code:
adb reboot recovery
More infos:
Android version:2.3
Kernel Version : 2.6.35.7 zjd@dtlinuxserver #45
Build Number fj_vortex-userdebug 2.3 GRH55 eng.zjd.20110824.115816 test-keys
Code:
adb devices
List of devices attached 
0987654321	device