You cannot convert a binlog to another version, but you import its SQL as long as have mysqlbinlog for version 4.1.

Simply do the following:

- Run MySQL 4.1 version of mysqlbinlog against the MySQL 4.1 binlog, saving output to stmts.sql
- Install MySQL 5.x with these in `my.cnf`
 - `log-bin=mysql-bin`
 - `binlog-format=ROW`
- Login to MySQL 5.1 and run `source stmts.sql`
- Run `SHOW BINARY LOGS;`

When done, the binlogs you see should be row-based.

Give it a Try !!!

Why can't you just convert ? The BINLOG Magic Number gets displaced with later versions.

I wrote about before

- `Nov 30, 2012` : http://dba.stackexchange.com/questions/29585/how-can-you-monitor-if-mysql-binlog-files-get-corrupted/29627#29627
- `Feb 04, 2011` : http://dba.stackexchange.com/questions/12530/mysql-master-binlog-corruption/12531#12531

Every time you restart mysql, the next empty binlog is created. Each version of MySQL has a different size:

- MySQL 5.6 : 120
- MySQL 5.5 : 107
- MySQL 5.1 : 106
- MySQL 5.0 : 98

In light of this, generating binlogs from scratch is the best way to go.