If the EnumProcesses succeeds, the return value is nonzero. If the function fails, the return value is zero.

So the 1 returned is a good sign :) not a failure.

Messy stuff, some functions return a positive number as a success, some return negative, no rule actually.

Check MSDN description for this function:
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/perfmon/base/enumprocesses.asp