Previously (Prior to v1.4) the Subversion server (svnserve.exe) couldn't be natively run as a Windows service. You had to use a wrapper such as srvany.exe from the Windows res kit to host it. Well now as of v1.4 it will run as a service but you have to manually install it. Doing this is pretty simple; just use the sc utility to add it at the command line as follows. The first svnserve switch (--service) notifies it that it should communicate with the SCM. The second (-r), which is optional, allows you to specify the root repository path.

C:\>sc create SubversionServer binpath= "\"C:\Program Files\Subversion\bin\svnserve.exe\" --service -r  e:\Subversion\RootRepo" displayname= "Subversion Server" depend= Tcpip start= auto

C:\>sc start SubversionServer

You can find the release notes about this new feature here.