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If iTunes isn't installing due to an error, the steps in this article can help:
Trouble installing iTunes or QuickTime for Windows
First try the steps in the "Additional troubleshooting" section of the article before attempting to reinstall iTunes again.
The installer has encountered unexpecting error ntalling this package. this may indicate a problem with this package. The error code is 2330.
The 2330 result is consistent with disk/file damage. The first thing I'd try with that is running a disk check (chkdsk) over your C drive.
XP instructions in the following document: How to perform disk error checking in Windows XP
Vista instructions in the following document: Check your hard disk for errors
Windows 7 instructions in the following document: How to use CHKDSK (Check Disk)
Select both Automatically fix file system errors and Scan for and attempt recovery of bad sectors, or use chkdsk /r (depending on which way you decide to go about doing this). You'll almost certainly have to schedule the chkdsk to run on startup. The scan should take quite a while ... if it quits after a few minutes or seconds, something's interfering with the scan.
Does the chkdsk find/repair any damage? If so, can you get an install to go through properly afterwards?