I'm sure this question has allready been answered on the forum - you should really search. But because you are new and I want the brownie points...

Log in as administrator (dont think you need technical rights)

Activate developer mode (you can search to find out how to do this

Go to a customer form

Change the value of what you want to make default eg county = United Kingdom

Select from the developer mode "set defaults"

Choose the default from the drop down

Select who you want the default to apply to.

Save default

I had one reference link where you can see how to set default country via code.

It might be batter option for dedicated solution.

http://snippetbucket.com/2013/07/openerp-set-default-country-by-_default/

Or you can set default as above option suggest, but it might again require to configure with new database.