The farthest back you can go with System Restore is 90 days...if you
have a restore point that old. However, even if you have a restore point
that old, you should generally /not/ restore it. Here's why:
1. System Restore is designed to restore the operating system, not
applications like iTunes.
2. Restore points contain a small selection of key system and user
account files. If you restore a very old restore point, your operating
system will contain a potentially unstable mixture of new and very old
system and user files. This could lead to crashes and other
unpredictable problems.
If you're having trouble with iTunes, describe your problems in a
newsgroup for iTunes.