Please help, my iTunes dissapeared and can't be reinstalled

Please help,.... there was a message "Apple upgrade" on my computer, and while it was upgrading, I opened the iTune and try to create a playlist from the mpg player, it was working, but when I closed playlist and try to click the iTunes it said the file is corrupted and have to reinstalled. I try several times to download to reinstall but it always said that the iTunes set up(3) exe is not a valid Win32. I check the Support and a suggestion to uninstalled iTunes to be able to reinstalled. I followed that instruction, but it failed, and the complete message is as follows: C:\Documents and Settings\Admionistrator\Local Settings\Temporary Inernet Files\Content.IES\9N298QSE\iTunesSetup(3).exe is not a valid Win32". I am using window XP. I tried to connect my iPad II, but it doesn't work.

Please let me know how I can get the iTunes again.Thank you.