The usual way to reset a Folder Type View Settings is as follows:
Open Explorer > Folder Options > View tab > Reset Folders OK > Apply/OK.
However, Vista keeps forgetting the folder type view settings. This occurs because by default, Windows Vista is set to remember folder view settings for only 5000 folders. (In XP it was 400, but has been increased in Vista it is 5000.) The way out is to increase this value to, say, 10000 folders. You can do so as follows:
 
Open regedit and navigate to
HKEY_CURRENT_USERSoftwareClassesLocal SettingsSoftwareMicrosoftWindowsShell
In the RHS pane, rt click > New > DWORD (32-bit) Value > Name it BagMRU Size.



Next rt click BagMRU Size > Click Modify.



Select Decimal and type 10000 (or in Hexadecimal base type 2710). Click OK. Reboot.