i want install Windows XP after Install Ubuntu 9.04

Are you absolutely certain that Windows was destroyed and your data was lost?

What is the error that Windows XP gives you during installation?

Is there "not enough room" on the drive perhaps? I am assuming from your problem description that you have deleted Windows and Ubuntu is taking up the entire hard drive. If that is the case then you will need to reformat the hard disk when re-installing Windows.

The Windows XP installer can do this, on the screen that selects "partitions to install" you can press "L" to delete partitions. Delete all of them and install Windows on the "Unpartitioned Space".

This will destroy all of your data, so be careful that you know what to delete if you have any important data on the machine. Since you are unfamiliar with this procedure, if you have any data you would like to keep you should use Ubuntu to copy that data to a backup.

Like what Ryan Makie said you could boot off the ubuntu
CD and when you get to the "How would you like to partition
your hard drive part." See if it recognizes Windows XP if so then you know
Windows is there so you can restart or press cancle. If not
click the option that says: "Manuel" then see if there is another file system (eg. NTFS or FAT32).
If so then windows is there. Then restart (and take the disk out of drive) or press cancle to stop installtion.

That is how you can find out if Windows is still there.

Hope it helps,
sam