I have a problem with my internet connections. I have tried all I know but couldn’t solve it. Is there someone kind to give me a tip, plz?

My internet connections work ok, but don’t accept changing settings or adding any new connection. It gives Error 624 when trying changing settings, or says some files are missing when trying to set up a new connection. But when I check up all files are there. Even so, I replaced those files with new ones from the original Windows XP CD. No way, doesn’t work. I have uninstalled and reinstalled the internet connection with the CD without any result. Now I need to replace my DSL connection with a new one and can’t do it.

Is there any sympathetic soul to help me on this stress? Thank you for any welcome help.