I am putting this here because I had a lot of trouble finding help with this issue also.
1) You may be working with a Volume License (did you get it from you school/business or did you buy it retail?).
If this is the case, you DO NOT need to deactivate/reactivate anything with your version of CS3, all you need to do is uninstall/reinstall.
2) If you are unsure, I found that the Help Chat was relatively pain-free: http://www.adobe.com/support/contact/, just choose your topic and select "Chat with an agent". They will need the serial number (hopefully there is a slip of paper in the back of your CD case with the number or else you recorded it somewhere) and they will be able to tell you what kind of license you have.
Note: This only applies to when the Deactivate option is absent, and not when it is greyed out, which seems to be a different issue.
Message was edited by: AustinOla
The two items...
- Download elicense...
- Return elicense...
fill the space where the Activate and Deactivate options appear, so you should look into why you have those options instead and see if you need to make use of the second of the two.