I'm planning to take my used mini Lenovo tower desktop computer & its 21" monitor from Abu Dhabi to india (Bangalore.)

Should I pack it in its original company boxes or should I pack both monitor and pc inside a carton box?

Should I have to pay customs? I don't have the original bill.

Edited If not packed on original boxes is this going to be flagged as suspicious like explosive upon departure ? or during the arrival when unoriginal box passes through x-ray custom will mark it or investigate ? In order to avoid all these embarrassing situations what's the right way.