If you are planning to upgrade you PC from Vista to Windows 7, you have two basic options: an Upgrade install, or a Custom one.
The Upgrade install seems like the obvious choice, and like the easy one. But it's not the smart choice.
An Upgrade keeps all of your settings and programs. In theory, you can just run the install and you're done.
But reality isn't so simple. You might get lucky, but you probably won't. Chances are that things won't work the way they're supposed to, and you'll spend a lot of time trying to figure out what went wrong. Problems may keep popping up for weeks. I've yet to do an Upgrade install that didn't end in me giving up, and starting again from scratch with a Clean one.
By the way, the Upgrade isn't even an option for XP users.
A Custom install gives you a clean copy of Windows 7. After the installation, you will have to recreate your user accounts, reinstall all of your applications and utilities, and change settings. That consumes time, but not as much as you'd likely spend tracking down problems with a Update install.
Before you do a Custom install, collect everything you need to reinstall your programs. Gather the CDs and DVDs. For the programs you downloaded, make sure you have license numbers.
Next, just to be safe, create an image backup of your hard drive. You'll need an external hard drive, and some image backup software. Macrium Reflect and EASEUS Todo Backup are both easy, dependable, and free. Either one will do.
Then boot from the upgrade DVD and do the install. When you're done, create your user accounts and reinstall your software.
You'll find your data files, and all of the other files from your Vista installation, in the C:\Windows.old folder. Obviously, you'll want to move your documents, music, and other data files into their appropriate Windows 7 Library folders. This is a simple matter of dragging and dropping.