R U kidding? Whatever possessed you to do such a thing?
Well you need to find out what the word "English (United States) looks like in Farsi (I think that's what the langauge is normally called, not Persian).You may also need to find out what words are used for OK and Cancel and learn to recognise them.
Then go back to the dialogue box that allows you to change GUI language and find the Farsi word for English. Hit OK...
Frankly I didn't even know this option was available in XP - I thought it was introduced in Vista.
If you are totally lost you need to go to an Iranian forum and ask for help with the language.
Nobody here can help you beyond tellling you where the language changing functionality is.