Do registration entries override stuff in the registry?

[gmod101]

I got a new computer YUY
And i backed up the registry for my softwares in RegEdit so i was wondering that if
i opened the backup registry file does it replace the registrys thats already there?
or does it just add the registrys that isnt there
NID HALP PLZ
And also you guys didnt solve my eclipse problem so
i had to rewrite some of the code again :l