It gets so annoying when someone checks in code into the source control that doesn't compile, don't you agree?
Unfortunately VSS doesn't have support processing of rules on check-in and doesn't force users to add a change log entry either. What? No email notification either? This sucks.
That's where TFS comes in... it has a bunch of additional features and is Microsoft's answer to open-source solutions such as CVS and SVN. For more on TFS, there's a page on MSDN comparing the features of TFS and VSS here: