The CAPI generator is, um, of variable quality. I cover one version in
http://www.cryptoapps.com/~peter/06_random.pdf. Note that the code appears to
have changed over time, and is now considerably improved (the details will be
in the updated version of the above paper). I don't know in which versions of
Windows the improved versions appeared, or what the specific improvements over
time may have been.
You can of course submit a patch to use our own prng, seeding it also
with CAPI data, of course ]=)