Some more thoughts on this issue:
The comments about the file system permissions being unpredictable are dead right. If you're working with folders and files used by other apps or people then you're flying blind and anything can happen. File might vanish or appear, drive letter unmapped, permissions can change, etc. I normally tackle the question of "do I have file system permissions?" at install time. I have a Custom Action that runs the ICacls command as necessary during install, so my code trusts the installer and assumes that it has permission to write to where it expects to. If it can't, then it's a serious problem in the environment or a human error. Avoid the problem by only writing to known folders with known permissions as specified in the Environment.SpecialFolder enumeration. I haven't tried using the System.Security.AccessControl <http://msdn.microsoft.com/en-us/library/system.security.accesscontrol.aspx> namespace for this specific purpose, but it has all of the ACE and ACL wrappers that can probably tell the real truth about whether you can read, write and delete from a folder. You'd still have to defend against timing problems and external interference. Greg
