There have been complaints about iTunes slowing down computers for years.
Looking back at the Apple Support community, I see many different reasons. Here is one that seems to continue to be an issue today. This one is from 2012.
J_Fish says iTunes slowed down his computer so much that he couldn’t use it. As I read through his issue, I see that it was a problem of iTunes constantly trying to connect and his anti-virus stopping it.
Many anti-virus programs are memory hogs. We recommend Webroot as it is the smallest yet most effective anti-virus/malware software in the market. You can get this along with some other benefits cheaper than going directly to Webroot if you go to www.WickedEasyFix.com
If you just updated iTunes to 12 you may have noticed, things have changed. iTunes added a bunch of programs that run in the background.
Here are our Top 5 ways to speed up your iTunes for Windows
1. Disable Unused Services
Open iTunes and go to Edit \ Preferences.
Then click the devices tab and uncheck:
Look for remote speakers connected with AirTunes
Look for iPod touch, iPhone, and iPad Remotes.
Look for Apple TVs.
Look for shared libraries.
2. Delete Smart Playlists
Delete the smart playlists, like Classical music, Jazz, etc... You can still create your own playlists and they will not slow down performance as much as the Smart Playlists.
When deleting a playlist, you’ll get a message asking if you’re sure. Check Do not ask me again and continue deleting the default playlists.
3. Disable Genius
Genius does a lot of things in the background. If you turned it on, shut it off. Click on the Store tab at the top and then Turn Off Genius. It will ask you if you’re sure…You are.
4. Turn Off Cover Flow
Cover flow may look nice, but flipping through album by album is old school.
Use the standard browser view which is a very quick way to find the collections of certain artists you’re looking for.
5. Remove Duplicate Files
It is likely that you have duplicate files on the same songs if you have a large library.
Just click File and then scroll down to display duplicates. Be careful that you don’t delete another version of the song with the same title. The easy way to check is to look at the time column. If the time is exactly the same, it’s probably a duplicate.