Here are some of the windows tools that can be used when working on window internals.

Autoruns (autoruns.exe) – http://technet.microsoft.com/en-us/sysinternals/bb963902.aspx
Access Chk – http://technet.microsoft.com/en-us/sysinternals/bb664922.aspx
Dependency walker – http://dependencywalker.com/
List DLLs – http://technet.microsoft.com/en-us/sysinternals/bb896656.aspx
Handle Viewer – http://technet.microsoft.com/en-us/sysinternals/bb896655.aspx
Logon Sessions – http://technet.microsoft.com/en-us/sysinternals/bb896769.aspx
Process Explorer – http://technet.microsoft.com/en-us/sysinternals/bb896653.aspx
Object viewer – http://technet.microsoft.com/en-us/sysinternals/bb896657.aspx
Service control – sc.exe (built-in tool)
Task Process List – tlist.exe (built-in tool)

Windows Tool package – http://www.microsoft.com/downloads/details.aspx?FamilyId=49AE8576-9BB9-4126-9761-BA8011FABF38&