2003 4.4 X5 no crank no start

[dgtal]

Please help. The problem started when I removed the battery cable to install a new alternator. When I finish and reinstalled the battery, it started fine. Then I tried to reset the oil/service indicator with not luck, I interrupted the procedure and screwed it up . I ended up killing the Air Conditioning. I disconnected the battery overnight and everything came back to normal. Except from time to time it did not start right away. I started using the immobilizer code "0000" in this forum, and it was working perfectly. Like 2 days later, she started without the code, 3 days later it did not start at all, no noise nothing. I left it for 4 days in a Mall close from our house. I tried every day 2 -3 times until one day it started. Well it was perfect for 10 days until about 8 days ago. It did it again, it is dead. Battery is ok and fully charged, I removed the positive to let the computer reset, nothing. I don't know what to do. How can I reset it. Do I have to try the procedure posted here about the oil/service indicator?