On Windows 7, My Documents is shortened slightly to just "Documents". You can access it from the new Start menu - there's a link in the top right corner.

The Documents folder is inside your user profile... usually "C:\Users\Your_User_Name\Documents".

There are no differences related to where files and settings go between different editions of Windows 7, so in general you can trust that you don't need to find Ultimate-specific documentation for stuff like this; Ultimate includes additional features but doesn't really change any existing ones.
The equivalent of "Documents and Settings" is now "Users", typically "C:\Users". Inside there will be a folder with your username, typically "C:\Users\Your_User_Name" - this is technically called your user profile folder.

There's a convenient shortcut to your user profile folder - you can just use %userprofile%, which will resolve to "C:\Documents and Settings\Username" on XP and "C:\Users\Username" on Vista and Win7.
http://support.microsoft.com/kb/287070 might be helpful to you in answering questions about migrating your outlook.pst file. You can actually put Outlook.pst anywhere you want, although it does have a default location in your Application Data folder.

The easiest way to open the Application Data folder is to hold down the Windows key and press R, then type and click OK. Once there, open the Microsoft folder, then the Outlook folder and you should find your .PST.

The exact path differs by platform but it's always under your user profile - on Win7, the default is "C:\Users\Your_Username\AppData\Local\Microsoft\Ou tlook\outlook.pst".
Hope this helps!