I have no clear answers, and there are numerous things that can contribute to such a thing, and you are certainly not alone here, a search shows many with the same issue, and the general consensus appears to be iTunes is whack, so other than turning to alternate software here are some things that may contribute to this.
Start with checking for any updates in iTunes, make sure you have the latest version.
Check how much free space on your hard drive there is, if it is too full this can seriously slow you down, I can't recall the ideal amount of free space, but 70% is probably as full as you want to be, a bit less ideally, so if your drive is pretty full try and clear some space, and uninstall unused programs.
How much ram do you have ? depending on the answer to this it may be worth checking your virtual ram.
Before launching iTunes, give it the 3 finger salute (press Ctrl + Alt + Del at the same time), click on the processes tab, then at the top of the CPU column, click on the words CPU, do this twice, once will bring the least amount of use to the top, twice brings the most used processes to the top, now launch iTunes and take notice of what resources are tying you up the most, this may show another item along with iTunes which may suggest it is fighting with it.
Try running some junk file cleaners, and maybe a defrag, it could be you have lots of residual files built up, I suggest the following tools if you don't already use them, and the reason for more than 1 junk file cleaner ? because I find each gets stuff the others don't, so this gives the max amount of cleaning:-
Disk Cleaner
CCleaner; Take special notice of the check boxes during the install (true of ANY install), and remove the bottom check box, unless you want the Yahoo toolbar.
CleanUp!; xp only.
ATF-Cleaner; This download link is very subtle, so make sure you click on the file name in red in the text about the program, you wont see any obvious link for this one on that site.
Auslogics Disk Defrag
See if any of that helps, then we can see if there is anything else that can help, worst case would you consider using an alternate program ?
There are several that can be used in place of this, and maintain the ability to sync to iPod's etc.
