Out of the box, the Windows 2003 Adminpak tools do not run on Windows Vista. When they are loaded, MMC claims that "MMC could not create the snap-in.". This is due to some DLLs not being registered properly. To fix this, paste the following commands into a command prompt or batch file running with elevated privileges (right click and "Run as Administrator"):
regsvr32 /s adprop.dll
regsvr32 /s azroles.dll
regsvr32 /s azroleui.dll
regsvr32 /s ccfg95.dll
regsvr32 /s certadm.dll
regsvr32 /s certmmc.dll
regsvr32 /s certpdef.dll
regsvr32 /s certtmpl.dll
regsvr32 /s certxds.dll
regsvr32 /s cladmwiz.dll
regsvr32 /s clcfgsrv.dll
regsvr32 /s clnetrex.dll
regsvr32 /s cluadmex.dll
regsvr32 /s cluadmmc.dll
regsvr32 /s cmproxy.dll
regsvr32 /s cmroute.dll
regsvr32 /s cmutoa.dll
regsvr32 /s cnet16.dll
regsvr32 /s debugex.dll
regsvr32 /s dfscore.dll
regsvr32 /s dfsgui.dll
regsvr32 /s dhcpsnap.dll
regsvr32 /s dnsmgr.dll
regsvr32 /s domadmin.dll
regsvr32 /s dsadmin.dll
regsvr32 /s dsuiwiz.dll
regsvr32 /s imadmui.dll
regsvr32 /s lrwizdll.dll
regsvr32 /s mprsnap.dll
regsvr32 /s msclus.dll
regsvr32 /s mstsmhst.dll
regsvr32 /s mstsmmc.dll
regsvr32 /s nntpadm.dll
regsvr32 /s nntpapi.dll
regsvr32 /s nntpsnap.dll
regsvr32 /s ntdsbsrv.dll
regsvr32 /s ntfrsapi.dll
regsvr32 /s rasuser.dll
regsvr32 /s rigpsnap.dll
regsvr32 /s rsadmin.dll
regsvr32 /s rscommon.dll
regsvr32 /s rsconn.dll
regsvr32 /s rsengps.dll
regsvr32 /s rsjob.dll
regsvr32 /s rsservps.dll
regsvr32 /s rsshell.dll
regsvr32 /s rssubps.dll
regsvr32 /s rtrfiltr.dll
regsvr32 /s schmmgmt.dll
regsvr32 /s tapisnap.dll
regsvr32 /s tsuserex.dll
regsvr32 /s uddi.mmc.dll
regsvr32 /s vsstskex.dll
regsvr32 /s w95inf16.dll
regsvr32 /s w95inf32.dll
regsvr32 /s winsevnt.dll
regsvr32 /s winsmon.dll
regsvr32 /s winsrpc.dll
regsvr32 /s winssnap.dll
regsvr32 /s ws03res.dll
Thanks to Microsoft employee Steve Linehan for posting this info on the ActiveDir.org mailing list.
UPDATE - There is now a KB article on this: http://support.microsoft.com/default.aspx/kb/930056