SQL 2008 multiple Registry entries in 64 bit server

I have installed SQL Server Express edition 32-bit on my 64 bit Server 2008 system.

I have found that multiple Registry entries are created in both WOW6432Node and 64-bit registries.

Is Microsoft creating both the keys by default or is it an error(from the package)?

If Microsoft creating those registries, please let me know the Reason

Thank You