Even if you had an installer, you can't activate it. After 15 years, it's time to get new software.
As @John T Smith said, Photoshop Elements is affordable and a major step up from what you've been using.
Another option would be the deeply discounted Photography Plan bundle for USD $10/month x 12 months. Everything a digital photographer needs and more: -- Photoshop CC and Photoshop for iPad -- Lightroom on desktop, mobile and the web -- Lightroom Classic -- Free Portfolio website + hosting -- Spark with premium features -- Bridge -- 20 GB cloud storage (upgradable to 1 TB). https://www.adobe.com/creativecloud/photography.html
Nancy O'Shea, Adobe Product User & Community Professional Alt-Web Design & Publishing ~ Web : Print : Graphics : Media