Noob question regarding restoring a router config

[BHPCI_2]

I have a 3845 router and the only backup I have is a 'show run' that was  copied and pasted into notepad.  If I try to paste this in to the router, it  only merges with the running config instead of replacing it.  Using my TFTP  server, can I just do a 'copy tftp startup-config' naming the backup.txt file as  the soiurce file or does it need to be in a format other than .txt?  Thanks in  advance. 

[Dan-Ciprian Cicioiu · Accepted solution]

Hi ,

Via tftp , will be enought : copy tftp://ip/file nvram:startup-config,then reload.

Or configure network tftp://ip/file

It doesnt metter the extension of the file , but it has to be a txt file - as you save it via notepad.

Dan