I am not sure if this has been covered in another thread but thought I'd like to point it out in case it helps anyone...
I finally moved my development machines to Windows 7 this past week and tried to install 5.2.1 on a clean Windows 7 (Ultimate) with SQL Server 2008 as the backend server.
I was expecting to find some issues especially since 7 uses IIS 7.5 (So does W2K8 R2) and ran into the normal issues which I believe Cathal has already blogged about on this site...

NETWORK SERVICE/Default Application Pool  Permissions
In IIS 7.5, the Default App Pool is set to run under ApplicationPoolIdentity - this is different from Network Service Account which we're used to in prior versions.
When you fire up your DNN website after a clean install, you're get a cryptic error which can be resolved in two ways
a) Change the app pool to run under NETWORK SERVICE and give NETWORK SERVICE read/write permissions on your website folder
b) Leave the App Pool as is and modify the security permissions to give read/write access to DefaultAppPool account. Unfortunately this account is not "VISIBLE" if you look up the accounts list on your machine and you have to type "IIS AppPool\DefaultAppPool" and do a search for that named user. See Cathal's blog about this.

There seems to be something on my machine which is causing DNN to fail installation in Internet Explorer 8. I can install the product fine on Firefox without any errors but can't get past installing 05.00.00 script without a failure notification. If I choose Automatic Install, this problem does not surface which makes me believe there is something amiss somewhere in IE 8. I can now reproduce this exact same behavior with another machine running Vista

Hope this helps someone :)