Format inside sdcard, tablet won't boot

[Casbia]

Hi all, I reformat the inside sd card in my mhk-801 android tablet in two partition like the guy how sold me the tablet told me to do to start like new. But the problem is, the tablet does not boot, I think by reformating the sd card I totally erase the android os. How do i install the android 2.2 OS on my sd card from my computer.

Help please

Thanks
Andre