can someone give me instruction how to install snow leopard (retail DVD) to lenovo ideapad S10-3. i have external usb dvd drive. at the moment am trying with iboot & multibeast method but no luck.

What exactly are the problems you encounter? A more in depth description might give you some more answers. Also please specify your hardware a bit more.

with iboot, i get the apple logo with white screen for long time after install dvd in dvd drive, doesnt seem any loading activity.

lenovo s10-3: atom n455 1.6ghz
1gb ddr2 ram
250gb hdd
not sure if this correct (some sort of pine.... graphic)

Can you boot with -v (verbose) to see where it hangs? Maybe post a screenshot of the hanging position so we can see what is going on.