I looked into these, and they seem to work rather well. I considered adding them to this module, but there were a few things that made me decide, ulimately, not to:

1. RtlGenRandom is available only in W2K and WinXP; and there are rumours that it will not be available in the next generation(s) of Windows. There are still a great many Win98 installations out there.
2. If I use /dev/random for UNIX and RtlGenRandom on Windows, I've solved two OS issues. That's great for my current project, but the personal goal I had when developing this module is to be general-purpose and platform-independant. I wish to avoid special cases when possible.
3. I see this module as an alternative to OS-based PRNG's. If someone is developing a tool that requires a good PRNG, I would expect them to use the best PRNG for the job. In other words, I want to leave it to the end developer to, say, prefer /dev/random first, RtlGenRandom, then this module if neither of the former are available.
4. The seed doesn't need to be very random, just hard to guess or duplicate based on general information about the system (the pid and/or the current time are bad, since loggers can guess this information closely enough to significantly narrow a brute-force search). The seeder I have now is so-so in this regard: it should stop anyone who doesn't have root-access to the machine from guessing the seed.
5. If you already have a good PRNG, you don't need this module anyway. ;-)

In short, I envision the use of this module like:

my $prng;
if ( -f '/dev/random' ) {
   $prng = sub { get_rand_from_file('/dev/random', shift) };
}
elsif ( ## Find out if RtlGenRandom works ## ) {
   $prng = \&rtlGenRandom_rand;
}
else {
   require Crypt::Random::ISAAC;
   $prng = \&Crypt::Random::ISAAC::rand;
}
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I do appreciate your pointing me to those references, though, as they will help with performance on a project that is Win2k-only.