QUESTION RELATED TO NT

Here are some knowledgebase questions, try and answer them..
1. ServicePack4
There are 2 versions of it. One is 40bit security and other is
128bit.
Q: How can you find out what version is installed on a desktop?

2. How can you remotely change a Local Administrator password without
going to that desktop. How many ways can you do this?

3. What does Regclean do?

4. How would you configure a DHCP for two subnets and more with
single NIC card?

5. You forgot the CD-Key of NT OS. Where can you find it on your
desktop with NT OS loaded?