Sounds like you need to study up a bit bud. This is skiddy stuff and you're trying to support clients.

Start here:
http://www.microsoft.com/learning/mcp/default.mspx

Plan to study for several months just to become adequate at supporting MS stuff.

I realize I'm being a jerk, but as stated above...it's just honest. You can't expect to adequately support clients if you don't know how to get ahold of a product key or reset a password here and there....or use an OEM disc.