Last year (Dec 06) I built a computer and everything was running fine for the first 7-8 months. One day after I switched my computer off, and tried to restart it, it wouldn't start. - System starts, I hear the fan of my gfx card spin up and the monitor remains blank.
Now normally, when it starts, the graphics cards' fan spins really fast, then it slows down (I can tell by its noise). However when it fails to start, the gfx card fan just continues to spin really quick, without slowing down.
In order to get my computer to start, I would have to take the battery out of the mobo, wait for 10 secs etc, put it back in, and when I start my computer, it would start normally (then reconfigure cmos bla bla bla).
Now the problem is that it happens whenever I shut my computer down totally. Each time the power to the computer goes off, I would have to take the battery out (reset cmos) for it to start normally after that. However, if I do not shut my computer down, but instead leave it on standby mode, everything's fine when I start it back up from standby.
I just took my computer apart to check to see whether there could be any connections which weren't right. I assembled it, and I had the same problems.
< Take battery out>
Computer starts perfectly.
Computer fails to start. (graphics card fan spins really fast and fails to 'slow down').
In order to get it to start, I would have to take the battery out of the mobo.
Sounds like your cmos batter is failing, you might be able to pick up a replacement at a local computer shop, b/c according to what you are saying, it loses your settings and you have to reconfigure everything at each boot. That's here I think I'd start, should be a cheap fix if it works, and if not, then you know it's possibly the board itself since you already did the reflash.
Ating frosty may be right about motherboard could be your problem?
I had the same problem your are having about a year ago with a asus p5nsli board,e6300, fan on gpu would stay on full throttle,shut pc down wouldn't power back up,pulled cmos battery wait 5 minute,booted right up but,noticed gpu fan still at full throttle.after about a month of trying different thing rma the board,received motherboard back did same thing,took motherboard out and found the mark I had made on mobo before sending it for rma,it was same asus pn5sli board I had sent them. long story short ending I throwed it in the waste can.the board I have now not 1 problem after 8 months. so it could be motherboard if you have excess to one may try that .hope this helps you