Make your factory Recovery Disks if you don't have them, so you have a path back to factory condition in case of resale, hardware servicing, etc.
Back up your data, gather your program installers, boot the Windows 7 DVD Repair console or Repair CD, press Shift F10 to open a Command Prompt, type:
SELECT DISK # (for Windows 7 disk)
clean all (zeros HD, takes about an hour per 320gb)
create partition primary
select partition 1
This wipes your HD to give the deepest possible clean, and to remove HP Recov and service partitions which won't be accessible after clean install anyway.
Now boot your Windows 7 DVD, select Custom to install to partition you've created.
The installer is mostly driver
complete, with newer drivers
arriving quickly via optional Windows Updates. Any drivers then missing in Device Manager can be found on the HP Support Downloads webpage for your model. Applications you want to keep can be extracted from HP Recov disks using this: HP 3rd Party Software After Clean Win 7 Install
Install programs slowly with Restore Points so that you can gauge performance changes. Remove any freeloading startup programs from msconfig as only AV and gadgets are needed to start up with computer.
When you have it setup as you want, run free state-of-the-art CCLeaner "Run Cleaner" and Registry tab then Auslogics Disk and Registry defraggesr. Then save a Windows 7 backup image externally so you never have to reinstall again, just reimage the HD or replacement in 15-20 minutes using DVD or Repair CD.