ACER MOBO Replacement

You'll have to find a Socket 775 mobo, I would look in the line of ASUS P5 series (they made a lot of them, P5Q, P5N, etc etc.) Try newegg and filter down to socket 775 then DDR2 RAM and get an idea of what mobos there are. You'll need something that supports your CPU, so make sure of that (not all chipsets support all CPUs). Any questions, link it and we can take a look.

For reference, the M5640-B5401A specs:
http://support.acer.com/acerpanam/desktop/0000/Acer/Asp...

Thanks alot, here one i just found. Just looked quickly but it looks like this one can do the job?
http://www.newegg.ca/Product/Product.aspx?Item=N82E1681...

That'll work perfect, has great CPU compatibility also so you won't have to worry about that...

Don't forget if you replace the motherboard that you need a fresh install of windows.

Good point Andrew, make sure you got a REGULAR version of Windows, changing your mobo will cause your restore discs to only have a 50/50 chance of installing. They query the mobo for certain things and if they don't find them (like SLIC), they won't install...

Thanks alot guys, much appreciated!!

So my processor will work fine in that new motherboard all i will have to do is reload windows?

Yup, your processor is fine in that board. Just have to reinstall Windows.