How can I restore IMEI code after factory reset? The phone is a Hero H2000 dual sim with Android v2.2.1, MTK Platform

I get an Invalid IMEI error after a factory reset.  How can I fix this?
There are several possibilities. The first starts with checking the "Related" section to the right of this page, which gives you some good candidates which already contain answers/solutions, e.g.:


How to fix “Invalid IMEI ” after Factory reset?


Next, there are some video tutorials on Youtube on this topic, e.g.:


How to Change or Repair Your IMEI Number On Android Cell Phone
HOW TO SOLVED Invalid IMEI


My short Google Search also found some forum threads providing hints and solutions, e.g.:


Invalid IMEI after Reset to Factory Defaults


I couldn't verify any of the mentioned solutions myself (luckily, I've never been affected by this problem) -- but I hope at least one of them will prove helpful to you.