From a span of Kindergarten to 7th grade (A span of 1996 to 2003), I used none other than an NEC Powermate VP75. For a 75Mhz Pentium with a basic video card and a retail edition of Windows 95, I was surprised how far I could push it; getting it to run games that it didn't even meet the minimum requirements for and have them still run at a playable speed. Also, it's very reliable; even when a local tech guy said that PC would never work again, I always managed to get it to come back to life with ease. I still have that PC, and it actually works much better than it did when we first got it (I made a few upgrades since it was passed onto me).
From 7th grade to 9th grade (2003-2005), I used this total piece of shit the local tech guy built (Ugly case, a 166Mhz AMD-K6 with barely enough RAM for Windows 98 to function with all the pointless stuff loaded into RAM we didn't need, several device conflicts, and many other things wrong with it). As much as it pained me to retire my trusty old NEC as the primary PC, I needed something with more power, and after I worked out it's problems myself (Against my Mom's better judgement, who felt more comfortible taking it to that same crappy tech guy who seemed to spend more time deleting our software and going through our personal files than actually fixing the problem), it wasn't too bad of a PC.
In my late 9th grade year until graduation (2005-2009), it was replaced with my own custom PC built in much the same way as the previous one, except this actuially turned out surprisingly well; being extreamly reliable for a 400Mhz Celeron running on a copy of Windows ME that happened to be on the hard drive I put in it (It's now in it'd 3rd version; with a 600Mhz Pentium III running on Windows 2000). It was great, though I faked it's death to get my parents to buy something new (It worked quite well, as I continued to use it for years while they used their own PC).