Did you use a registry cleaner recently? If so there may be backups you can try to restore.
Also system restore may be an option if it is a problem that occured recently, did it?
Do Search or Help work from within Explorer, can you bring up the run dialogue by pressing Windows key + R or from taskmanager - file - new task?
Originally posted by jumpy I don't know about the others but for help and support just check that the Help and Support service hasn't been turned off. Control Panel -> Admin Tools -> Services -> Help and Support.
If it's not that, well i think a system restore should fix it. Or a windows repair if it comes to that. There would be no harm in running the system file checker.