I cannot get my i phone 4 to sync with i tunes. It tells me the required disc cannot be found.

This symptom may be caused by an issue with the digital signing of Windows XP drivers. Following the steps below to reregister the several .dll files mentioned below may resolve this issue. Before attempting the steps below, try to restore the iPod using the latest version of iTunes. If you are unable to restore the iPod or if the symptom reappears, follow these steps:

1. Disconnect the iPod from the computer and close iTunes.
2. Highlight all of the following 10 lines of text that begin with regsvr32 and then choose Copy from the Edit menu of your web browser: regsvr32 /s softpub.dll
   regsvr32 /s wintrust.dll
   regsvr32 /s dssenh.dll
   regsvr32 /s rsaenh.dll
   regsvr32 /s gpkcsp.dll
   regsvr32 /s sccbase.dll
   regsvr32 /s slbcsp.dll
   regsvr32 /s mssip32.dll
   regsvr32 /s cryptdlg.dll
   regsvr32 /s initpki.dll
   
   
3. Open the Notepad program by navigating to:
   Start > All Programs > Accessories > Notepad
4. In Notepad, choose Paste from the Edit menu. Note: Make sure that the text that appears in Notepad is the same as what is shown above.
5. From the File menu, choose Save As.
6. For File name, type appleipod.bat and save the file to the Desktop.
7. Close Notepad and locate the appleipod.bat file. It should appear on the Desktop with the icon shown below:
8. Double-click the file and you will see a black window appear on the screen for about a minute. Wait until the window automatically disappears and proceed to the next step.
9. The appleipod.bat file can be deleted at this time.
10. Open iTunes and connect the iPod.
11. When the iPod appears in iTunes, restore the iPod and resync your content.

Note: Because some malware may unregister the .dll files, make sure you have the most recent updates to your anti-virus software and then do a full scan of your files.
Solution 2This symptom may also be caused by software applications which change the appearance of Windows XP. Try deleting or removing any third-party Windows OS skins, Windows themes, or desktop mods that are installed to resolve the iTunes Error -50 issue when syncing your iPod to Windows XP.