The sweet spot for W9x/ME is 256Mb of RAM.
Most people should agree with that.
Anything else above this is a waste of time.

Windows NT/2K/XP pretty much like as much RAM as you can chuck at it.

NT4/2k can handle dual processor setups.
But having two processors will not double your power, like many people think.
The app must support SMP (multi-threaded).
Even then performance might not live up to much.

I did think Windows XP Pro also supported SMP though.

Anyone know if it does or not?