Overlocking issue

Have you stress tested after you overclock? Made sure your CPU, GPU etc. isn't overheating?

If your overclocking and don't understand how/why your bus/RAM speeds change, or don't know how to stress test, STOP OVERCLOCKING. Not only will overclocking void any warranty you have/had, you can DAMAGE the devices in your computer. Do more reading, ask questions, but don't just start changing values in the bios.

You can stress a CPU by running an instance of Prime95 on each core. (info is here. http://www.playtool.com/pages/prime95/prime95.html) You might also want to run memtest86 as well.

Actually, that isn't true. Many motherboards (mine included) will happily push voltage to levels that are well above the recommended maximum if you overclock with the voltage on auto.

I'm doing it in Bios(Asus M3N-H/HDMI has such options like Overclock 1%, 8%,10%).
Voltages and other settings set to 'Auto'. RAM frequency set to Maximum Clock.
At 10% Overclock, CPU charges to 3.3GHz from 3GHz. And RAM's each 412MHz(i.e, total 825MHz). When no Overclocking is done(At 3GHz), RAM speed is 750MHz. I think it need to show 800MHz at no Overclock(coz. they are PC2-6400 RAMs).

+1. Prime95 is a very popular overclocker's stress tool.

well, the reason the ram isn't running at DDR2-800 with your processor at stock is because the ram speed is tied to the cpu speed, you have to take your cpu **** and divide it bye the muliplier divided by 2 rounded up (so 15 / 2 (rounded up) = 8, 3000 / 8 = 375 or DDR2-750)

I've enquired about Blue Screen Troubles at Asus Technical Enquiry dept. They say my mobo and processor are not compatible with each other... I'm using Athlon64 X2 6000+ Windsor(125W) on Asus M3N-H/HDMI. They say its not compatible with 125W version... only compatible with 89W version of the same processor.. Well..i've read technical spec on M3N-H/HDMI as, it support 125W processor.
http://in.asus.com/products.aspx?l [...] odelmenu=2

That could be the problem. If the motherboard only supports up to 89W CPUs and your using a 125W CPU, then overclocking, the motherboard won't be able to handle it. You said you can run it stock, do that until you can afford a better mobo/CPU.

I'm not sure why they said it won't support it, as you can run it stock and it says it can. I still get the feeling that although it can run it at stock, overclocking is stressing the board to much. If 125W is right at the upper edge of what it can do, it won't be able to handle a 125W CPU trying to suck even more power in OC'd mode.