Don't know if you got things resolved, but after an hour or so I got DNN 4.5.0 run fine with Vista Ultimate 64 bit, IIS7, and SQL 2005.
I did the following:
1. Created a new application pool for DNN sites. Set it to run in classic mode (not integrated) (its set in IIS manager)
2, Created a new directory and loaded in the install release
3. Adjusted the DB connection string in config.sys
4. Added a new application in IIS manger that points to the new site directory and set it to use the DNN app pool
5. Make sure that your permissions on the directory are set to allow .NET access (for my local system I give my directory right o everyone with read /write (this is my desktop so its secure)
6. Run the install by going to the new folder directory in a browser. Follow the prompts.
If you run into a message that say you need to migrate this app into either integrated or classic, choose the classic . Open a cmd window with Admin rights (i do it by going to accessories and right clicking and choose run as admin, don't use the run command) paste then run the command line that is listed on the error page.
You should be good to go.