As long as you are running a 64bit version of the OS.
Running a 32bit OS with more than ~3gb RAM installed is pointless.
Oh and hard drives are slow yet still need to be accessed so buy a fast 10,000RPM drive or an SSD.
Indeed. Always 64bit unless you're on a netbook or something.
The key thing with hard drives is only to have to access the buggers once, which means no memory pressure, ever. I find 2x7200rpm SATAs in a mirror is pretty good. Doubled read speed and losing a drive doesn't involve reinstalling the machine. Most Linux distros will do the setup for this in the installer now, too.
Indeed. Always 64bit unless you're on a netbook or something.
The key thing with hard drives is only to have to access the buggers once, which means no memory pressure, ever. I find 2x7200rpm SATAs in a mirror is pretty good. Doubled read speed and losing a drive doesn't involve reinstalling the machine. Most Linux distros will do the setup for this in the installer now, too.