First you should check to ensure your PC is capable of running Windows 7. Go to
click here download and run the check software.
Before you start installing Windows 7, ensure that you have backed up all your data and that you have all your software DVDs, printer and other hardware drivers etc. as you will need these after the installation is complete.
When you run the Windows 7 install, unless you tell it otherwise, it will completely wipe your existing C: drive before starting the install - the alternative to this is possible but I would not recommend you try it.