Blank page on upgrade to 2.7- admin goes to other blog

I will never ever ever believe that there is any easy upgrade in WordPress. THERE NEVER IS. It never works. Info is sparse, errors common, etc.

Trying to upgrade from 2.5.1 to 2.7 through ftp. I read many instructions. Looks easy, isn’t. First, many errors, then a white screen.

I had disabled all plugins. I backed up. I moved over wp-admin and wp-includes. I was afraid to move over wp-content, for fear it would override my content. Then I read here that I should move over some. (although I see now, in this page that I shouldn’t have deleted wp-config. I’m sorry.)

At this point, when I go to mycurrentblog/wp-admin/ it logs into ANOTHER OF MY BLOGS which I also used 2.7 in. There is nothing in htaccess to forward one blog to another. Is there a file I can change so it lets me input my old login words, or is that gone?

Please help!