I don't like the Windows. One of the reason is that the registry goes wrong after installation some applications. In fact, registry is not a great design. When you install software in Windows, there is no guarantees that you can 'completely' uninstall it afterwards. From my experience, something must be left in registry and it will be forever until you reinstall the Windows later.
So anything can help? Sure, and the answer is so called 'Portable Application'.
From my understanding, Portable Application is orginally designed for storing application in USB flash drives, with configuations file store in files instead of registry. Therefore, the applications do not depend on the Windows registry and can be installed anywhere.
One successful example is the PortableApps.com, it releases dozens of free application which can be installed in a USB, or any directory of the hardisk (including USB/IEEE1394 external hardisk, of course). Another advantage of using portable apps is that we do not need the administrator rights to install those applications. For example, I do not have administrator account to the PC in my company, and Internet Explorer is the only browser installed. Too bad right? But now I can download Portable Firefox, and click the exe file, then I can use Firefox without installing to the system.
Apart from Portable Firefox, there are also other applications which are useful. There are IM, Email client, Media Player and even WebServer! Please refer to the reference below and I am sure you will find some good applications for you.
Ref:
http://en.wikipedia.org/wiki/List_of_portable_software
http://portableapps.com/