You follow below steps to repair or restore Windows XP.
Steps:
1.Insert windows xp CD in your CD drive.
2.Then Restart your computer.
3.Then Press Any KEY to boot into cd.
4.Then in blue screen say, "To set up Windows XP now, press ENTER”, you press Enter Key.
5.Then ACCEPT the License and Agreement by pressing F8 key.
6.After that in blue screen give the three options To repair windows xp installation using recovery console ,press R.Accept this and you Press R key.
7.Then the Set up is DELETING all your Windows XP® files and replacing them.

You follow below steps to repair or restore Windows XP.
Steps:
1.Insert windows xp CD in your CD drive.
2.Then Restart your computer.
3.Then Press Any Key to boot into cd.
4.Then in blue screen say, "To set up Windows XP now, press ENTER”, you press Enter Key.
5.Then Accept the License and Agreement by pressing F8 key.
6.After that in blue screen give the three options To repair windows xp installation using recovery console ,press R.Accept this and you Press R key.
7.Then the Set up is deleting all your Windows XP® files and replacing them.