It all depends on your needs. For running basic 32 bit apps., a 1 Ghz system is still adequate.
However with the newer 64 bit technology now on the scene, many new apps. are sure to follow. It will be over a period of years, but most will have to upgrade.
Like you, I have an older 1.1 Ghz Dell Dimension 2100, that's in use at my office. I received notice today, from the software software supplier (that I use for business), that they will be upgrading the program. I will receive the newer release at no extra charge. It's faster, with many more tools and options.
The only problem is that my trusty old Dell is already at minimum requirements. That means if I want to use the new program, I'll have to upgrade to a faster machine. It's been very reliable for over six years, but it looks like retirement for the old boy.
I bought a refurbished Dell P3 1 Gig a few years ago. I think it was about 2000 or 1999. I'm still using it. It still works fairly well. I added 256 meg of memory for 512 total and now use Windows XP. I think I can use it for at least another 3 or 4 years which may be 10 at that point in time. It had just about everything on it that was recommended at that point in time, DVDROM, 1394 IEEE Firewire, USB,and memory. I'd say if you get somrthing with a similar configuration today withenough memory, a nearly new processor chip, DVD & burner, HD, warranty, etc., you could get 10 years out of a Dell refurb. They usually are new computers that were returned and not used much if at all and then get checked out to meet new specs. Generally, it's been a good experience with this pc and I think I've gotten a little more usefulness out of it than I thought I would.

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