This batch will tell you where backups will go by default. It works on SQL 2000 and SQL 2008 for me:

[font="Courier New"]declare @data nvarchar(512);

exec master.dbo.xp_instance_regread

N'HKEY_LOCAL_MACHINE',

N'Software\Microsoft\MSSQLServer\MSSQLServer',

...

I wanted to come up with a solution of my own with reading just the statement of the challenge. So, here it is. I took me about 10-15...