Fresh install of WP 2.6, while keeping old install

So after reading the codex about moving wordpress:

https://codex.www.ads-software.com/Moving_WordPress

I have a few questions about my specific situation. I am looking to do a clean install of WP 2.6 for my site, https://www.shutterscript.com; however, I want to be able to access the old site and give a “hidden” URL of the old site to people who would still like to access it. I don’t want it to be indexed by any search engines or to be made publicly available.

Originally I was thinking of moving the old installation to something like https://www.shutterscript.com/old, but for some reason that doesn’t strike me as a good idea.

Another thing I’m worried about is how search engines will index and rank my new site (with far less content initially) once it replaces the old one. This has me considering forgetting the clean install completely and just hiding the posts I don’t want on my site. If i hide about 100 posts and recreate most of them how I want, would this adversely impact performance? I keep drawing a paralell to reformatting HDs… they always run better, am I right in assuming the same for WP?

Any suggestiosn on how to approach this would be appreciated.

Thanks