If you are using vista or xp and now thinking of upgrading then, we would suggest you to go for it. Windows 7 is much better OS than vista and xp in any way, it is much more performance oriented operating system and if you want to try before you upgrade you can check out Windows 7 Test Drive.
Microsoft has a web application interface which allows you to test and run windows 7 directly from your browser. This website is launched by Microsoft to provide the live preview of windows 7 and to show case all the new features windows 7 has like aero snap, aero peek, libraries, version control, enhanced troubleshooting etc.
As shown in the above interface you can test Windows 7 from your browser, see how does it work through walkthroughs and training videos available and learn more about increasing productivity, enhancing security, and cutting costs with Windows 7.
Note: You Need a Windows Live ID to use Test Drive Windows 7
Check Out – Windows 7 Test Drive