Windows is over 30 years old, so this is a good time to look back at the five most important Windows releases of all time. Note that this is not a list of the best Windows releases, but rather the releases that were the most important. It’s been a long, strange journey, Microsoft.

Chances are you’ve worked on a Windows XP computer at some point, which is why it’s on this list. XP was popular and had a long lifespan. Windows XP, released in 2001, still has a larger global market share than Windows 8 or Windows Vista. It dominated the market for years, and that longevity speaks volumes about how good XP was.

XP was an early success, despite an early misstep. It wasn’t until Service Pack 2 that Windows Firewall, the primary security tool, was enabled by default. This delay contributed in part to Microsoft’s reputation for building insecure products. Despite its flaws, XP had many advantages, which accounted for its remarkable popularity.

Windows 95, released in August 1995, marked the moment when the public began to embrace Windows. Microsoft launched a massive public relations blitz for Windows 95, highlighting the introduction of the Start button, unveiling it to the tune of the Rolling Stones' "Start Me Up." Perhaps in an ominous sign of things to come, Microsoft co-founder Bill Gates was shown a Blue Screen of Death during a Windows 95 demo.