This article will take you through the process.
But essentially copy the iTunes Folder and all sub folders on to your new computer and paste it in the right place
Locate the following folder on your new computer:
Mac OS X: /Users/username/Music
Windows XP: \Documents and Settings\username\My Documents\My Music\
Windows Vista: \Users\username\Music\
Windows 7 and Windows 8: \Users\username\My Music\
For photos, these are not sored in iTunes so you will have to copy them over separately then use iTunes to sync them
On the new computer if it is not authorised with your wifes Apple ID then they will not play and you will have to delete them unless she gives you the Apple Id and password. Then you can autorise the new computer with that ID as well as yours and all the music will play
That's not entirely true--most music from Itunes isn't protected with a DRM anymore. In any case, you probably don't want to use your wife's apple ID anymore. Best bet is to create your own apple ID and copy the folders as Steve Taylor1 suggested. If any of them give you a msg saying that you don't have the rights to play them well, legally, you would have to buy them again. If not, no problems. Now, movies on the other hand would be quite a bit more tricky, and basically you can't copy them to a new account legally. There are all sorts of ways to do this illegally, but I won't go in to that since I can't condone piracy. If you and your wife are able to speak to each other civilly (hey, it happens in some divorces) maybe you can come to an agreement where she lets you use her apple ID, but otherwise this is pretty much where you're stuck.
I think both Steve Taylor1 and I are assuming that you were sharing an Apple ID before now. If that's not the case and you already have a separate account, then anything you purchased with your account would be yours, so just make the copies and you should be good.
Photos are probably yours so you can make as many copies as you want. I couldn't tell you where you stored them, but most of the time they're stored under the photos libraries, both on Windows and OSX computers. Sometimes they'll be stored under the name of the software you used to download them from your camera. You can try searching your harddrive using searches like this "*.jpg" which will locate all files with .jpg extensions, but not all cameras save as jpegs. So without having access to your computer, I can't promise you this will help you find all of them. But like Steve Taylor1 said, once you copy them to the new computer, just go into Itunes and add the folder in which you copied them and they'll be in your new library.
All of that clear as mud? Hope your divorce goes smoothly and you're able to enjoy your newly single life!