[bongos_man]

most of the code that was available is for tools that have better free/open source replacements these days. but here are some links to the old tools & whatever code was provided:

http://court.shrock.org/sysinternals/
http://court.shrock.org/sysinternals-bt/
http://web.archive.org/web/20060427210005/www.sysinternals.com/SourceCode.html (also check out the rest of the site)
https://github.com/xcud/sysinternals-source

in fact the official microsoft code samples are quite good as well, you will not find undocumented api info of course but they are quite comprehensive.

https://code.mdsn.microsoft.com (check the "desktop" box to filter out non-windows junk)
https://github.com/Microsoft/Windows-driver-samples good kernel reference material here