Post date: Dec 21, 2011 10:29:12 PM
IIS 6 typically uses a standard Windows account called 'Network Service' to execute ASP.NET code. This implies that if you want QBO configuration pages to save changes to the file system, the Network Service account needs write permissions to the subject files.
IIS 7.5 and later gets a bit trickier, though more secure. By default, each Application Pool executes under a virtual account (e.g. 'IIS APPPOOL\ASP.NET v4.0'). Just like with Network Service, you will need to explicitly grant permissions to this account to write to the configuration files. However, the subject account is not listed under the list of user accounts. (It's a, ahem, virtual account.) No matter, simply type the name into the Select Users or Groups permissions dialog, and Windows will accept the virtual account name.
For QBO 3 installs, security must be granted to web.config and the Config folder to modify file(s). To configure:
Obtain the name of the application pool used by the website. From IIS, if the name of the website is qbo.localhost.net, look the the Application Pools tab and see which application pools are listed. Chances are there is a matching application pool named qbo.localhost.net. As a result, the virtual account name would be 'IIS APPPOOL\qbo.localhost.net'.
From Windows Explorer, right click on the root folder of the website and choose Properties ->Security Tab
Click Edit, then click Add
Input IIS APPPOOL\qbo.localhost.net into the text box and click OK
The name qbo.localhost.net will now appear as a listed account under the previous security tab
Grant write and modfy permissions
Repeat same steps for Config folder
Read more on the hows and whys of IIS using virtual accounts.