Q: error 5105

Try turingtest2's reply on this thread : Re: Itunes last version present 5105 error

You have given very little to go on. Clearly Mac iTunes - but versions of OS X and iTunes are conspicuously missing from your report

Advanced steps for fixing issues with iTunes Store connection - Apple Support

in future, refer to this for posting a question

We need much more information to give you specific help. Tell us step-by-step, in detail what your actions are.

Tell us a Story

- with a beginning, a middle and end. We need to understand everything that you know and have experienced.

If this issue is new, tell us what immediately preceded its onset - add software, upgrade or update? New equipment?

Quoted from  Apple's "How to write a good question"

   To help other members answer your question, give as many details as you can.

• Include your product (device) name and specs such as processor speed, memory, and storage capacity. Please do not include your Serial Number, IMEI, MEID, or other personal information.
• Provide the version numbers of your operating system and relevant applications, for example "OS X 10.4.11" or "Safari 4.1.3".
• Describe the problem, and include any details about what seems to cause it.
• List any troubleshooting steps you've already tried, or temporary fixes you've discovered.

For a detailed "coaching", please see the User Tips Help us to help you on these forums and Writing an effective Apple Support Communities question

"Keep It Short and Simple" - Take your time... but be thorough - ÇÇÇ

You have given very little to go on. Clearly Mac iTunes

There is a windows button bottom left of the screenshot, windows icons bottom right of it, and the icons top left and top right of iTunes are from windows

Woops!

No wonder all the search results referred to Wndoze!

https://www.google.com/search?q=error+5105+itunes+windows+site%3Aapple.com&ie=utf-8&oe=utf-8