Is it possible to convert Bitcoin Miner to Litecoin Miner? I have 90Gh/s Bitcoin Miner and its almost useless for Bitcoin Mining with current difficulty. By changing the Linux software installed in it can I convert this Bitcoin Miner to Litecoin Miner? I am capable on uninstalling/flashing the current operating system and re-install a new one but I am wondering is it just software that decides to mine only Bitcoin or hardware too supports only Bitcoin Mining?

If not possible with Litecoin Miner can I use this miner for mining any other crypto-currency?
No, you can't. And this has nothing to do with the operating system. Your hardware has a bitcoin ASIC chip made only for doing Sha-256 calculations. Litecoin uses the Scrypt algorithm. Sha-256 and Scrypt are not the same, so what you are suggesting is impossible.

You can mine other Sha-256 coins instead of Bitcoin.