because you told it to insert into the trigger_original table... not original...

Code:
INSERT trigger_original(Roll,UserName,Password)
SELECT ROLL,Name,Name+'124'
FROM INSERTED
It did exactly what you told it to do...

That said... it is DANGEROUS to insert into the same table you're triggering off of... you could end up in an endless loop that could cause the system to crash...

-tg