Like a double edge sword, editing your Registry could be fun or full of woes! Use caution and make sure you know exactly what you are doing. Always backup your Registry before editing it, unless you are an expert, and need not bother with the backup.
To edit the Windows Registry, click Start, Run, and type in regedit

• HKEY_USERS\.Default\Software\Microsoft\Internet Explorer\Main
• find the Window Title key, right click and choose Modify
• enter whatever text you like, and click OK

• HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion
• modify RegisteredOrganization key
• modify RegisteredOwner key
• click Start, Settings, Control Panel, System to view your changes

There are countless things that you could do with the registry: setting your desktop appearance, how Windows starts up, how each program runs, where to look for a CD, etc. Be aware that when you unintall a program, the keys in the Registry may or may not be deleted. Over time, Windows will eventually become sluggish. The only solution is either do a clean Windows reinstall, manually cleaning the Registry yourself (stay away from this), or get a program that cleans the Registry.