I have an SBS 2011 machine with C drive running out of space. Looked up this guide which helped save 5GB of space. Essentially it reduces the size of the WinSxS folder after SP1 has been installed. Took about 10 minutes to run, just make sure you wait until you see a message that states the command has completed, not just 100%.
- Open an administrative command prompt
- cd \windows\system32
- dism.exe /online /cleanup-image /spsuperseded