I think that today I finally figured out what was going on with my desktop. So here is the story:
I have a desktop that was running Windows XP. I bought it to play games (as you can't really play many games on a Mac) and to run the occasional software that either doesn't have a Mac version (e.g. CadSoft's Eagle, or has a much worse Mac version (e.g. Intuit's Quicken).
A lot of the games that I was playing I bought on Steam, which meant that they took a lot of disk space. Moreover, I was starting to be annoyed with the gradual lack of support for drivers and other things for Windows XP. So I decided to take the "hit" and to a double upgrade: (1) Buy Windows 7 and (2) Buy another 2 TB of HD.
Actually it was cheaper to buy two 1 TB HD, so that's what I did. So I now have 3 HDDs on my desktop and Windows 7. And everything seemed to be running ok. Until one day that I woke up in the morning and my computer was off without me turning it off. As I turned it back on, it stopped "mounting" one of the new HDDs! It could recognize it, but it just wasn't there to be used anymore.
I was puzzled, but had to do other things. When I came back to my computer: off again. And this time when I turned it back on it didn't turn itself completely. I had to turn off again and on again and everything seemed to be working for a few hours and it would shut down again (never when I was using it, though).
My first thought that it was some sort of sleep mode, but one piece of evidence that suggested otherwise was that Windows complained that I turned off the computer unexpectedly when it came back. So I dropped that theory.
My next theory was that the power source was too weak for 2 new HDDs. I couldn't figure out how to prove it, so I bought a new bigger power source that arrived today (well, actually yesterday). After installed, I turned the computer back on and everything seemed normal, except that the HDD was still not being added. Tinkering around a little I found that it was simply not being assigned a name and fixed that.
I went out for dinner and when I arrived back the computer was still on! Very exciting! Then I went to watch the Top Chef final episode and when I arrived back to my computer... Surprise! It was off! I cursed it and turned it back on. New surprise: it came back on in the same place it was before! My computer had gone to sleep! Then everything clicked! This is what I think happened:
* By default Windows 7 puts your computer to sleep after 30 minutes in idle.
* However, my old power source did not support sleep mode, so when it would issue the sleep message, it wouldn't sleep exactly, it would just turn off.
* The new power source does support it, so it went to sleep as expected.
I turned off the "sleep in 30 minutes" and not I'm going to sleep myself and see in the morning if my theory is correct.
The conclusion is that maybe I shouldn't have bought a new power supply... It's also debatable whether I should have bought Windows 7. I have to agree that it was great that it automatically recognized my network printer, while for Windows XP it was extremely painful to get it to only half-work (I couldn't get the scanner to work at all and the printer printed every other request). But my video card that has only the latest upgrade for Windows 7, is still showing the same rendering bugs that I was seeing before.
I'll write more about Windows 7 some other day. It's certainly not as "refined" as some people claimed, but it's cleaner and prettier than XP. Also, it doesn't feel any slower than XP. And that's all I can say for now.