A while ago, I got a job as a video editor for a video gaming site. This job required a system with a lot more power than the one I had, so my then boss shipped me one they had previously used for a few years for the same function. It was a bit of a clunker Pentium D, but it performed a lot better than my own rig, and I also had to pay for it as if it were knew, because of it's outrageous video card (8800 ultra).
For a while, things went well, it could do the work in a reasonable amount of time, and heck, I had a dual core machine and all I had to do was work for free for a few months. Well, not the best idea I ever had, but that's besides the point. After about half a year, it started doing things. It would on occasion freeze up when playing Team Fortress 2( and no other game besides that), and sometimes, when I tried to start it in the morning, at 5AM, when my work day started, it sometimes wouldn't boot.
All the fans would be running, all the lights would be on, but until I turned it off and turned it back on again, (like the people at The IT Crowd thought me), it wouldn't boot. I didn't think much of that, mostly because I was afraid the boss would make me pay for repairs, and it continued to work, in spite of that strange behavior.
About a year after I started the job, actually, a year to the day since I got that PC, something else happened. I was playing League of Legends, having some free time on my hands, since the week before I had quit my job. As I was doing my best to bash people in the head with Mordekaiser, suddenly, the screen got corrupted, and the number of frames per second started to drop. A few restarts later, no game would run for more than a few seconds, before the screen became corrupted. I figured it was something to do with the video card, so I left it alone for a day. The next day, I didn't start any games, I just opened a video file, I was watching it, and then, the screen got corrupted again. It was definitive, the video card was borked.
I tried to take it out, and see what was wrong with it. Nothing was evident, since being a gigantic power guzzler, it had a huge plastic case, that covered the cooling elements. I popped it back in, and tried to start the PC again. It went through it's "won't boot" phase again, but this time, no matter how much I tried, it just wouldn't start. Tried for a while, and just gave up on it, since I couldn't afford a new video card, and I was on vacation. But then I got another, similar job, which sort of required a better PC. For a while I struggled with ye old PC as much as I could. I had adapted well to not being able to playback in real time anything I edit. Then, a miracle happened, I got a brand new Radeon 5850 from the "Your spell in Elemental Contest", that Stardock hosted while ago.
Things were going great, I placed the video card on a shelf, to admire it, and the day after my birthday, full of hope, I installed it. But the PC still wouldn't boot. Tried everything I could, and still nothing. A few weeks later, I passed it on to someone who had experience with fixing PCs, not just braking them. Sometime later, he brought it back, sort of working. He couldn't figure out what was wrong with it, after a while it just started to work. He brought it back, and it still wouldn't boot, guess it didn't like me. But after a while, it worked.
Since my second PC got fried over night, I developed the habit of unplugging it when I'm not using. So it turns out that after I plug it in, and switch on the PSU, I had to let it warm up for a few minutes in order to boot directly. I could try and start it up without that, and the fans were on full power, the lights were on, but no booting. If I did that about three times, the third time, the fans would slow down, the lights that didn't need to be on went off, and it booted up.
After a few more months of this, one day, while it was more or less idle, it stared to reboot. It happened once, I didn't think much of it, problems happen. It happened twice, in the same day. Then again, faster, more frequent, and then would just crash the second it got into windows. I managed to see it was somehow related to the voltage, well, at least it seemed to. CPU-Z showed some wild fluctuations in the CPU voltage, once the restart coinciding with the CPU slowing from 3.2 to 2.8 Ghz, in order to conserve power. It does that by default. I booted it up again in the BIOS, the voltage was constant, everything was constant, and it was stable. It was sort of stable even in Safe Mode, though I didn't do a proper reliance test. I decided to give it a rest, and I tried starting it the next day, and surprise surprise, it wouldn't boot. Fans on full power, all the lights, even the once that shouldn't be on, are lit, the keyboard gets power for a second when it boots, the mouse doesn't, neither did the CD Drive, and it's been doing that for two weeks now.
I have no clue what's wrong with it. The guy who sort of fixed it the fist time said it was probably a faulty connection in the motherboard, but I still hope it's something that I can fix.
If you're wondering, it's a Pentium D 935, on an Intel D975XBX2 motherboard, with 2GB of RAM, an SATA Seagate HDD, and an OCZ 650 PSU.
The best assumption on what's wrong with it that I have so far, is that it found out I plan to replace it later next year, and decided to throw a fit.
Has this ever happened to you?