Hi,
· What happens when you try to enable the add-ons?
· Which browser you are using?
If you are using Internet Explorer, you may follow this link & check if it helps.
How to manage Internet Explorer add-ons in Windows XP Service Pack 2
Refer: Internet Explorer add-ons: frequently asked questions
Note: This article is applicable for Internet Explorer 7 or 8.
Hope the information helps.
Please post back and let us know.