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The leak is due the pointer-type cache that ctypes.POINTER uses. The type the pointer refers to is used as the key. In this case, VS_FIXEDFILEINFO is created each time win32_ver is called, so the pointer-type cache grows without bound. Example leak:
 >>> import psutil, platform
 >>> proc = psutil.Process()
 >>> proc.memory_info().rss
 14704640
 >>> for i in range(10000):
 ... v = platform.win32_ver()
 ...
 >>> proc.memory_info().rss
 92704768
 >>> for i in range(10000):
 ... v = platform.win32_ver()
 ...
 >>> proc.memory_info().rss
 168861696
Clearing the cache followed by a collect() reclaims the leaked memory for the most part:
 >>> import gc, ctypes
 >>> gc.collect()
 333
 >>> proc.memory_info().rss
 168849408
 >>> ctypes._pointer_type_cache.clear()
 >>> gc.collect()
 740000
 >>> proc.memory_info().rss
 20303872
It's a moot point, since Steve plans to re-implement this check in C, but the minimal change to fix this leak is to bypass the pointer-type cache by manually subclassing ctypes._Pointer:
 class PVS_FIXEDFILEINFO(_Pointer):
 _type_ = VS_FIXEDFILEINFO
 pvi = PVS_FIXEDFILEINFO()
There's no more leak after this change:
 >>> import psutil, platform
 >>> proc = psutil.Process()
 >>> proc.memory_info().rss
 15450112
 >>> for i in range(10000):
 ... v = platform.win32_ver()
 ...
 >>> proc.memory_info().rss
 16592896
 >>> for i in range(10000):
 ... v = platform.win32_ver()
 ...
 >>> proc.memory_info().rss
 16601088