If you like to download a free application to replace Windows applications bundled with free alternatives, over time your right to find that in some cases there is not much benefit to be obtained. Therefore it is better if you reduce the number of third party software running on your computer.
Benefits of Microsoft software has more security and stability, although it does not look as striking feature is widely used as an alternative or at least you can trust that the freeware microsoft's certainly more secure. For that through this post I suggest you not to replace six windows that have been congenital tool from microsoft with other applications. :
1) System Maintenance
Windows Vista administrative tools, including many armed Disc Clean-ups, Spyware and Virus scanners and defragmenting.
If you are running Windows XP then you can use Windows Live OneCare online tools to scan your computer. This will scan for viruses, check your junk files, defragmentation, and system performance.
A beta version of Vista OneCare is offered free of charge here but I do not support computer system for several reasons,