Back up your files to external HD.
Follow the steps here to wipe the HD clean first so you will have the cleanest possible install: SSD / HDD : Optimize for Windows Reinstallation
Now reboot with the Win7 DVD in tray and it should autostart, install to the partition you made.
The Win7 installer is mostly driver-complete, with newer drivers arriving quickly via optional Windows Updates. You'll need to get online to get them, however, so be sure your wireless driver is backed up to external so you can install it if the installer doesn't. Find your wireless driver on the manufacturer's Support Downloads webpage for your computer model. If you use a wire, back up the ethernet driver.
After updating drivers from optional Windows Updates, look in Device manager again to see if any drivers are missing or in error with an (!) exclamation mark. If so, download and install those drivers from the computer's Support Downloads webpage.
Install programs slowly over time to gauge any performance changes. Don't let any programs write themselves into the msconfig>Startup list besides AV and gadgets as they freeload on CPU/RAM and can spy on you. Use a lightweight free AV like MS Security Essentials or Avast 5.
When it is finished, clean and order your HD perfectly using state-of-the-art CCleaner and Auslogics Disk and Registry defraggers. Then save a Win7 backup image externally so you never have to reinstall again.
Locate Device Manager, msconfig, Windows Update by typing in Start Search box.