If you want to feel old, consider the fact that Windows 95 launched 20 years ago today.

Although the operating system was a major success for Microsoft, it also had an enormous impact on Apple — both good and bad. Here’s how Cupertino responded at the time.

Despite the fact that the scales were firmly tipping in Microsoft’s favor, Apple engineers didn’t worry too much about Windows 95 when they first heard about it.

Before Windows 95 hit shelves on August 24, 1995, Cupertino employees rode around with car bumper stickers reading, “Windows 95 = System 7” — likening the new Microsoft O.S. to Apple’s then-4-year-old Mac O.S.

When Windows 95 arrived, Apple mocked it with a full-page ad in The Wall Street Journal reading, “C:\ONGRTLNS.W95” — a dig at Microsoft’s long-running DOS system.

But Microsoft’s monster success did have a big effect on what one former Apple employee described to me as the “Apple psyche.” For one thing, Microsoft had built an O.S. that wasn’t a million miles away from what the Mac offered at the time.

“Microsoft was delivering a ‘look and feel’ which, while we threw rocks and said, ‘It’s not as good as ours,’ there was a fear that it was good enough that everybody who used Macs because they were easier to use, would then be able to say that Windows was just as easy,” Apple’s former director of human interfaces Mitch Stein told me when I was writing my book The Apple Revolution.

Interestingly, another ex-Apple employee claims Windows 95 changed the way Mac interfaces were designed. Having previously had market researchers tell engineers that users wanted muted colors on-screen, Windows 95 revealed otherwise.

“We had this big crash course to make everything look sexier, to make it more colorful,” human interface engineer David Curbow told me. “I think it was the first realization that we were not just building computers for people. We were building things that would look good enough that you wanted to buy them.”

As one final piece of trivia, the product lead in charge of Windows 95, Brad Silverberg, started out his career at Apple as a programmer on the Lisa, straight out of graduate school. “I thought it was essentially game over for Apple,” Silverberg told me, recalling his thoughts about Windows 95 at the time. “I didn’t see how they could compete.”

Fortunately for us, he couldn’t have been more wrong.

Two years later, Steve Jobs was back at the helm and the rest, as they say, is history!