First, 32-bit is old school nowadays.
Second, XP is old school and if not replaced with Vista, will most certainly be replaced by Windows 7.
Thirdly, 4Gb has become the standard IMO (I run 4Gb on my laptop, 8Gb on my desktop).
What is the reason why you wish to use 32-bit XP?
As far as Cooler Master products go... just 'cause you buy their case don't mean you gotta use their PSU. Go with Corsair, Enermax, TT Toughpower series, Seasonic, or other more reputable brands.
250GB HDD? What brand, what model, what size cache, what interface? Get a WD Black with 32Mb cache for good performance.