I have a website which is fully in html. I want to make it CMS because it is eeasier to maintain and more efficient. I have a few visits from Search engines now. If I make my website in CMS (with the same text) will it affect my SE visits? Worpress or Drupal for the cms?
It could effect it either way. Anytime you make changes to code you change content positioning and density. You aren't likely going to see a huge increase just because you went to a CMS. Off-page factors have much more of an impact with google. I would say you would likely be able to get more support and plugins with wordpress if you don't have a lot of experience and might require help. They are both very good.
Are you making any updates at all? If not, leave the HTML, since Wordpress and co. need constant upgrading (otherwise they are in risk of being hacked). Were you to go with a CMS, I agree with mjewel - choose Wordpress, it's better for beginners.
hmmm... you may need to check first if the link urls will stay the same after you move, or you'll have to make it so.
Drupal is overkill for a static -> CMS conversion. I would use MODx because it's easy and can keep your current page structure (it can Re-write the pages to be .html .htm .php or whatever you want). It's also very fast and easy to use. I would try this one. Wordpress is a bit more scatty, especially the editor which tends to have a mind of its own sometimes. It's not bad, not bad at all though.