The one I have is about two years old and already slowing down. I clear history, cookies and cashe regularly and defrag it about once a month. I really don't want to have to buy a new one right now.
I have to admit the last Windows powered computer I had ran Windows XP. In 2010, I bought a Mac Pro and haven't looked back since. It's the computer that I'm on now and it is still doing the job.
Initially, when I left Windows, I went to a Linux powered machine but the distribution that I chose wasn't as user-friendly as I'd hoped. I used it for a while and liked it a lot, but my computer skills weren't up to the task. So in 2010, I bought an Apple.