I have purchased an intel atom 6.75"x6.75" size mini-itx mobo and I need a case for it.rosewill offers a case with sizes 10.28"x7.87"x6.54",cube mini itx.but nowhere the fixing hole dimentions mentioned.I would like to know whether the fixing holes will match with the mother board.can anyone clarify?

ATX is the largest physical size mobo followed by the Micro. You wouldn't need to worry about anything smaller as they are more expensive anyway.
I would be inclined to replace the power supply also as that will be 'tired' and would probably struggle to power the new board. I never fit anything less than a 500 watt power supply. They're not that expensive anyway and it's always better to have power to spare than to be on the borderline.

GO TO SERVICES AND RESTART WINDOWS AUDIO.

you need a sound card then

If you change the Date and Time and when you next boot up your computer the Date changes to some previous date then the CMOS/BIOS battery is flat and it needs to be replaced. Most motherboard use a 3 volt coin size lithium battery type CR2032 you need to check which type od BIOS battery your motherboard uses.

no display

change the drive

http://www.intel-driver.com/Intel-drivers/s_349_1.html

there ya go
cheers!!

150 w is a bit low, especially if you have two CD or DVD drives, two hard drives, hi powered video card, LAN card, Sound card etc.
You should add up your power requirements of your devices and allow for a bit extra, If you run the power supply close to its limit it will not last.
I suggest you install at least 300 to 400 W power supply depending upon what you have installed in your computer.

Yes, you can, just that it will be really slow - the Atom processor is extremely weak. Just put the 1600 in, they will be automatically underclocked to 800.

go to intel to see for updates on drivers jim