you deleted some or all of your protected and hidden system files from the root directory, but it's not clear what you did because you mentioned 'activate' then changed that to 'delete', and you also change what you deleted from files to folders.
I assume you didn't delete any folders from the root directory, (normally called C:\ ), but only deleted the files there. However, if you also deleted the hidden system files like boot.ini, I am surprised your system still boots up into Windows. Can you check what is still there?
In Windows Explorer goto Tools > Folder Options, then the View tab. Make sure there are ticks to show all the hidden files and folders, including the Protected System folders and files, then Apply/OK.
Do any files appear under the C:\ directory? If not, how did you delete these?
You might try System File Checker, (SFC), from the Run command, (Start > Run, type in sfc /scannow (notice the space)), and click OK. Have your XP CD handy as SFC may want it. I am unsure if this will work for files deleted from the root directory though.