Digging around in our vast storeroom, we managed to find an old AMD Athlon machine that was just right at the border of the minimum requirements at 1.2GHz. Installation too was done similar to the P4 machine and took longer than expected due to the slow read/write speeds of the machine's ancient hard disk drive. We persevered though and soon after perhaps two hours or so, we had Windows 7 up and running too on the Athlon rig.
Sadly, our experience was hampered by the bottleneck of the hard disk drive. It could have been better but with a sluggish 20GB HDD that's running at just 4500 RPM, we were so out of luck. Also, stuff tended to slow down a tad at times as the CPU was stressed to full load during the simplest of tasks. But let's be fair here. If you're just using it for basic productivity needs and for Internet needs, you can do no wrong here as it's definitely more than sufficient. The fact that you could get Windows 7 running on an aging machine without any of the sluggishness that we've come to expect from Vista is something that we can jump straight into bed with.
Due to the limited hard drive capacity however, we were unable to set up a dual boot configuration to get the boot times for Windows XP and Windows 7. Windows 7 did take around 65 seconds, pretty close to the faster P4 machine that we tested earlier. Bear in mind however, that we didn't experience any sluggishness when using the other machine for basic tasks while we could actually detect some on the Athlon.
To see how far we could stretch the Athlon system though, we decided to underclock the processor and also remove half of the RAM, leaving the unit with a 931MHz CPU and 512MB RAM. On the whole, the unit performed pretty much the same as before, though the lack of RAM does make its presence felt when you open too many applications. We don't really advise anyone going on this route though. Sure it's possible but it's not really a good idea unless you just want a computer for the most rudimentary usage (like surfing the web).
Well wrapping things up, how low can you go with Windows 7? Pretty low it seems, but the lower you go, the more limited you will be by what you can do. We do think it's cool on how you can still smoothly run Windows 7 on some of the lower spec'd machines compared to Vista but of course, don't expect to bring that old 486 DX2-66 back to life. However, it certainly does give your older and probably decommissioned systems lying around in the storeroom a new lease of life by setting up a new home network to allow you to fulfill that long lost wish of surfing the Internet in the toilet and more (amongst other cravings).