How do i get my administrator privileges back on windows XP?

(long but important) ok so someone gave me a windows XP laptop as a gift , but i tried to erase everything that the original user had, and i was doing great , i had a lot of administrative privileges until i tried to delete this folder in the Document and Setting, and it didn't let me do it, so i tried to log in as an administrator but i didnt know how so i looked and looked until, i made the mistake of going to the control panel>administrative tools> computer management > users and groups> so i clicked on the the administrator folder and clicked on " user must reset password on next login", so now im stuck with my welcome screen asking for the password and having to press Ctrl+Alt+Del and login in to this guest account that doesnt have any rights i cant even download any programs or delete them. please help, how do i get my admin rigths back? (btw thanks for taking the time to read this and to help me)