This post hits the nail on the head with regards to the problem with the new Alt-Tab in Windows Vista. Win-Tab is quite cool and useful in which I will eventually move over to. But I want something fast and something that I can quickly find,hmmm much like in XP. In Vista, when pressing Alt-Tab instead of showing the icon of the application as in pre-Vista, this has been replaced with a very small image of the whole window which is too small to identify.
To restore the XP Alt-Tab functionality simply add a DWORD named AltTabSettings to HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer and set its value to 1.