I don't have the CD/DVD version personally but I would think by the info given that you would just install over the top (as Nova explains it - repair the installation)

What I would do myself for extra safety is to copy the game somewhere else first or rename the folder to save a bit of time.

Example:
Rename From "Delta Force Xtreme 2"  to  "Delta Force Xtreme 2 Backup"

Don't worry about registry entries.

You will probably have to activate again (easy, use your novaworld login) and away you go...