NET Interop and COM

1) How can we use COM Components in .NET?
2) Once i have developed the COM wrapper do i have to still register the COM in registry?
3) How can we use .NET components in COM?
4) How can we make Windows API calls in .NET?
5) When we use windows API in .NET is it managed or unmanaged code ?
6) What is COM ?
7) What is Reference counting in COM ?
8) Can you describe IUKNOWN interface in short ?
9) Can you explain what is DCOM ?
10) How do we create DCOM object in VB6?
11) How to implement DTC in .NET ?
12) How many types of Transactions are there in COM + .NET ?
13) How do you do object pooling in .NET ?
14) What are types of compatibility in VB6?
15) What is equivalent for regsvr32 exe in .NET ?