Accessing the registry from a web service

I've been having difficulties accessing some (but not all) registry keys from my web service. I therefore assumed (and confirmed with some research) that there are some security restrictions on accessing the registry. Is there some code or change in the configuration I need to do specifically in my C#.Net application?

Specifically, I am trying to read and write the values of the PageSetup under "Software\Microsoft\Internet Explorer\PageSetup"

After impersonation of the user HKEY_CURRENT_USER will be not changed. You should use RegOpenCurrentUser after impersonation of the user and RegCloseKey.

Alternatively you get the user's SID and read registry from HKEY_USERS:

WindowsIdentity wi = HttpContext.Current.User.Identity as WindowsIdentity;
if (windowsIdentity != null) {
    SecurityIdentifier si = wi.User;
    RegistryKey key = Registry.Users.OpenSubKey (si.Value +
                            @"\Software\Microsoft\Internet Explorer\PageSetup");
    // get some values which you need like
    string top_margine = key.GetValue ("margin_top");
    key.Close();
}