Installing 2 diffrent version Drupal sites on one Lindoe

Well after going deep into Linode/Ningx, without really knowing what I was doing i decided to see if the community might be able to help solve my issue the easy way.

I'm not it's here i should ask (or on a drupal forum,i'll try there too).

I have a Drupal 5 installation running a site that i need to have in the air and look after.

I want to instal an additional Drupal 7 site.

The D5 was set up by a company that knew what they where doing and is running Apache.

Should I:

1. get a new Linode and install (if so should I go for Apache or Ningx, which I sort of started messing around with.)?

2. use the same Linode 786 and install on a different directory a D7 installation.

2.1 what else do I need to instal (Apache, php things etc.)

2.2 I would need to by another IP address? and if so / or if not, how do I set it so I can point a domain to the new folder.

that's it,

I think that once I have all the answers I will be able to get this off the ground.

Thanks again for everybody's help with my last issues,

Tomer