This is a problem that started just within the last few days, though I think I had the same problem almost a year ago.
I leave my computer on 24/7- which I know it arguably a bad idea, but that's beside the point. During the day I work on it or leave it connected to the internet so I can remote-connect to it. At night I have it run Anti-Virus scans and do other long running tasks that don't require my attention or would otherwise get in my way during normal computer usage.
The problem is that once I come back to my computer after leaving it idle for a few hours, I get a black screen. To describe it further: the screen is totally black, no cursor or anything. Neither the mouse or keyboard do anything. The power button is still lit up and on front of my computer, the power and wireless lights are on solid. There is nothing I can do to bring the computer back to life. Pressing the power button one immediately shuts down the computer (just like if I were to hold the button for a few seconds).
When I boot back up, the BIOS tells me that windows didn't shutdown correctly and asks me to select a boot option (ie Safe Mode, Safe Mode With Networking). I always boot windows normally and it always comes up without any problems. When I log in it says that windows recovered from an unexpected shutdown and asks if I wan't to check for a solution. If I say yes, then it says "checking for solutions" for a few seconds, then the window disappears and I don't hear anything about it again.
Plugged into my computer I have USB-powered cooling platform (which I use because my computer overheats when I play games that require a lot of resources, particularly Skyrim). I have a tiny USB mouse receiver with wireless mouse. In addition to that I have the power cord and a CAT 5 cable for my wired internet connection. None of these things have changed in the last few months.
Here are the specs for my computer:
Windows 7 Home Premium SP1, 64 bit
Dell Vostro 3750 (around 4 years old)
Intel i7 CPU
Any idea what's causing this problem or how to fix it?