Can I install both drupal 6 & 7 in subfolders of public_html on shared hosting?

Hi friends!

I have a shared hosting account with Hostforlife.eu, and currently have maybe 6 or 7 drupal 6 sites installed there. Drupal 6 is installed in the public_html folder. I have a couple of Drupal 6 sites running in an multisite arrangement.

I would like to move most of the sites to drupal 7, but one or two cannot because of themes etc.Can someone point me to a document that lays out how to install drupal 6 and 7 in subfolders of public_html, or explain how it can be done?

I was told recently that you can't have both versions of drupal running multisite under public_html. So, I am willing to give up multisite. I don't know enough to be sure that this is so, but multisite may be more trouble than it's worth for the few sites I have.Is it true? Thanks it advance!