I went to install SQL 2008 SRSS on one of our webservers this afternoon and kept getting told that it was failing the reboot pending check. After a bit of digging this seemed to have been caused by a visual studio devel install leaving crap in the registry, namely;

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\PendingFileRenameOperations

Delete any value in the key then hit the rerun button and you are good to go.