Ok i am overclocking and I have the ASUS P5N-D motherboard. There is a setting in there that lets you pick your fsb speed and your memory speed separately so the memory doesn't go up proportionally with the fsb.I have ddr2 800mhz ram and I don't want to overclock it yet. Is this a good idea to not up the memory speed while the fsb speed increases?
It depends on the over all FSB you choose, as well as the divider, however, you should easily be fine with 415 FSB or so.
Depending on your processor type and multiplier, just be sure to set the memory divider mode to sync mode. So linked and synced will work, or unlinked and manually entered MAY work, hehe, Dependant on memory dividers. I have the same board, and while it didnt like 1600 FSB, it sure didnt mind 1604. For a 401 FAB total, and thats fine. It has the "seamless" stepping for memory dividers, which can mess things up.
To my knowledge, you don't set RAM speed directly, you set a ratio with FSB. If you don't want to OC the RAM, then yes, you will have to lower the ratio as you increase FSB, but being slightly over the rated speed shouldn't affect stability unless you have crappy RAM or really tweaked the timings tight.