I had this problem once before: Would turn on computer, would see the motherboard screen, and then I'd get a blank screen with a flashing cursor. I stuck in my windows install disk, and I couldn't do any kind of recovery or memory check, and the startup repair was kind of useless. Well, I rebooted after starting up in safe mode with the CD still in, took it out, rebooted again, and successfully got to that safe mode menu thing. (I'm very technically articulate, aren't I?) So, that was a good sign. I selected the debugging mode option for the heck of it, Windows started normally, and everything was peachy keen until I wanted to turn my machine off again a couple days later.
I'd been putting it to sleep every night for the past 3 days or so, and resumed Windows without any problems. Only when the computer was completely shut down did I run into this again. Except that this time, I can't access the safe mode menu thing at all without the install disk in.
So I did some more probing around this morning, did another startup repair deal, and decided to take a closer look at the results. Everything was fine, except that it said there was something wrong with the partition: "The partition table does not have a valid system partition." Also said that this issue was fixed, but... Windows still isn't booting.
I googled some, and found this thread, actually: Invalid system partition
The computer in question is still relatively new (about a month... first computer I've built myself) so I wouldn't be absolutely devastated if I had to reinstall the OS, but I'm trying to avoid having to go through the trouble of reinstalling all my programs and putting all the files back on. Anyways, I guess what I'm trying to say is that I'm willing to fool around a bit to fix this. So I tried what the very helpful posters on the above thread said to do in the command prompt. I was able to get to the bootsect menu, but none of the commands that the OP was told to do were recognized.
So... yeah. I'm at a loss. Should I just suck it up and reinstall? Or will that even fix my problem? What should I do? D:
EDIT- K major derp moment. I went back to try this stuff again. The command lines worked, but windows still won't boot. Fffuuuuu-