This kind of questions always popup when there is a new OS on the roll. So its time for Windows 7 and its right time to check if your computer can run Windows 7 and if your existing OS ( vista or Xp ) can upgrade properly.
Microsoft has released a Windows 7 Upgrade advisor, which you can download and run to get a report which can notify you of the any constrains for which your computer cannot run windows 7 or if any of the existing software installed is not going to work.
You can download a copy of Windows 7 upgrade advisor from here and read more information here
If you are upgrading from Windows Xp to Windows 7 , read more information about it at Migrate Windows Xp to Windows 7 : Video Tutorial