I am tryin to Replace the start of line with a \"(\". However when i use replace all i\'m not able to do so.
For eg:
432425\\n 4254645\\n w4546746\\n 464
I don't know why you are having problems.
This works for me in Notepad++ v6.2:
Search -> Replace Search Mode -> Regular expression Find What: ^ Replace with: \( Click Replace All