<p>How can I find out if SP1 has been installed on a server which has .NET 3.5?</p>

Look at
```
HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5\
```
. One of these must be true:
The
```
Version
```
value in that key should be
3.5.30729.01
Or the
```
SP
```
value in the same key should be
1
In C# (taken from the first comment), you could do something along these lines:
```
```
const string name = @"SOFTWARE\Microsoft\NET Framework Setup\NDP\v3.5";
RegistryKey subKey = Registry.LocalMachine.OpenSubKey(name);
var version = subKey.GetValue("Version").ToString();
var servicePack = subKey.GetValue("SP").ToString();
```
```