Hi and Welcome. My Name is ***** ***** I look forward to assisting you today with your question.
Your Mac is an "Macbook Pro Mid/Late 2007" and you are running a 8+ year old OS X. The latest one is macOS 10.12 Sierra
Your Mac can't handle the latest 10.12 Sierra however it can handle up to 10.11 El Capitan. The problem is, you need to upgrade to 10.6.8 Snow Leopard first and then upgrade to 10.11 El Capitan from 10.6.8 Snow Leopard.
So you need to buy the 10.6.8 Snow Leopard disc and upgrade to it --> http://www.apple.com/shop/product/MC573Z/A/mac-os-x-106-snow-leopard
When you get the Snow Leopard disc, just put it on your Mac and follow the onscreen instructions to upgrade. After upgrading to 10.6.8 Snow Leopard, click on Apple > Software Updates and do all updates.
After that, to install 10.11 El Capitan, click this link --> https://itunes.apple.com/app/os-x-el-capitan/id1147835434?mt=12
or install it from here --> https://support.apple.com/en-us/HT206886
This will take you to App Store with 10.11 El Capitan link. So click GET button and use your Apple ID and password ***** download it. Once it is downloaded, it will open the installer (will take a few hours to download) and follow the onscreen instructions to install it.
Note : Although upgrading won't delete any files, I'd recommend to backup your important files to an external hard drive or any other disk. Also, you will no longer have iPhoto in latest OS X. Instead you will see a new app named Photos. So open it and it will load the photos that were in iPhoto, if any.
If you have any questions or would like any additional information, please don't hesitate to ask.
Note : This is not my final answer. I strive to provide Excellent service or 5 star service. If you feel you've received anything less or if you are not satisfied or if my solutions didn't work, please don't rate me bad or poor or ok. Instead, please let me know and I will try my best to help you until you are fully satisfied or the issue is resolved.