The best thing is you should always select all the options, as these options are different from each other and scan for the invalid registry entries at different locations in the Windows registry.

The Max Registry Cleaner scans the invalid entries and deletes them as they are of no use to the user and take up unnecessary space in the registry. When you delete the detected entries the software takes the complete backup of the entries you delete so that they can be recovered is case of any emergency.

Whenever you wish to scan your Windows Registry, Max Registry Cleaner presents you with a list of different categories of registry entries that may be scanned. These are:

	Startup Program: Startup entries are registry entries that tell Windows which programs are running when the system is started up.
	Start Menu Item: Start Menu entries are registry entries that tell Windows which programs appear in the Start Menu - the menu presented to you when you click on the "Start" button.
	Shared DLL: This registry key contains references to shared DLLs (Dynamic Link Libraries). These are important files that are shared by multiple programs to reduce memory and disk space requirements. If Max Registry Cleaner cannot find a DLL file that is referenced in the Shared DLLs section, such a registry entry is flagged as invalid.
	Font: Max Registry Cleaner will find invalid font references in the system.
	Application Info: Max Registry Cleaner will scan the registry entries of applications(programs) that refer to various paths on your PC. If entries are found pointing to paths that do not exist on your hard drive, such entries are flagged as invalid.
	Sound & App Events: Max Registry Cleaner will scan Registry entries associated with sound files.
	Logged On User: Information related to the currently logged-in user is scanned.
	File Extension: There are entries in the Registry that help Windows use the right program to open any file with. For example, files with the extension ".doc" open with Microsoft Word. Max Registry Cleaner will scan the Registry for such file extension records that are associated with non-existing programs, or for programs that are associated with non-existing files.
	Shared Folder: Max Registry Cleaner will scan those entries for which a shared folder referenced from this section is missing or the specified path to this folder is invalid.
	Help File: Max Registry Cleaner will scan entries for files with the extensions ".chm" and ".hlp" and verify if the paths to such files are valid. If not, such entries will be flagged as invalid.
	MRU Entries (Most Recently Used Files): Max Registry Cleaner will scan your "Most Recently Used Files" list, and present a list of entries that you could delete.
	Empty Registry Key: Any keys that are empty (i.e., the key has no value) are flagged as invalid.
	COM/ActiveX: Before a COM/ActiveX object can be used by any program, a reference to this object must be created in the registry. If a registry reference describing a COM/ActiveX object points to a non-existing file, this reference is considered invalid.
	Deep Scan: If any registry values contain invalid paths, such keys are flagged as invalid.
	Windows/MS-DOS Shortcut : Registry entries for shortcuts (files with .lnk or .pif extensions) that point to other files or applications, may point to non-existent objects or icons. Such entries are flagged invalid.
	Cookie: Scans all cookies downloaded or created by Internet browsers like Internet Explorer, Mozilla FireFox and Netscape. It displays all cookie entries in scan from internet cache. These cookies are present on path e.g. C:\Documents and Settings\ UserName\ Local Settings \Temporary Internet Files and C:\Documents and Settings\ UserName\ Cookies for Internet Explorer on Windows XP and 2000. ((Here C: is the drive where your operating system is installed)) Note: These entries will not recover once you delete it from your PC.
	URL History: Your internet browser such as Internet Explorer, Mozilla FireFox and Netscape keeps track of all URL's you type into your browser's address bar. This is not the same as Auto-Complete URL's. You must click on the down arrow in your browser's address bar to find these URL's. Internet Explorer creates these entries in registry and other browsers add these entries to a file History.dat. After scanning URL History these entries are reported in to Registry cleaner UI in the form of registry entries or file. You can select particular entries for Internet explorer and History.dat file for other browsers and can delete URL history from your PC. Note: These entries will not recover once you delete it from your PC.
	Recycle Bin File: Whenever user deletes files and folders in Windows by pressing delete key or using mouse, by default files go in Recycle bin, and whenever user presses shift + delete those files and folders are permanently deleted from system. This option scans recycle bin and displays all deleted entries by user. You can select entries from registry cleaner and can delete them permanently. Note: These entries will not recover once you delete it from your PC.
	Clipboard: Coping any file, text or image consumes space on clipboard memory (temporary file).This clipboard memory can be erased by this option. Note: Contents of clipboard memory are not recoverable once you delete it from your PC.
	Windows Application Log : The Windows keeps information about what applications are opened by users in the form of Application Log. There are as many events in the application log as many applications are used / opened by the users. In Windows 2000/NT/XP, you can see the application log by typing - Start Menu>Run>eventvwr in run and viewing Application Log. This option will scan all the records from application log and displays no of records and memory consumed by application log. To clear this memory, scan and delete application log. Note: This option is not used for Windows 98 and ME. Because there is no Application Log present in Windows 98 and ME. Contents of application log are not recoverable once you delete it from your PC.