That board has a standard of DDR2 800 and supports OC's to 1066Mhz speeds, so yes, you could use 667 as well.
The lack of an IDE connector shouldn't concern you at all unless your using an IDE device. Most Optical drives/hard drives are now SATA II oriented so you should see no problems. Are you using any IDE devices?
As far as the processor support, it COULD support the 45nm chip out of the box depending on the BIOS revision. If it doesnt, then all it would need is a BIOS flash more than likely, but that would involve you having a spare 65nm chip laying around so you can boot up with it. Or you could buy a cheap Celeron off newegg or something.
This is the board your talking about, correct?
Newegg.com - Foxconn G43MX-K LGA 775 Intel G43 Micro ATX Intel Motherboard - Intel Motherboards