Please explain what you did when you installed Windows 7. There should be a folder called Windows.old where some of your previous information is kept. Unless you did an in-place upgrade from Vista to 7, you will have to re-install all programs.
This is only the case if you have done a windows upgrade to 7, not if you have done a fresh installation.
Going by what i can decipher of the original post, win 7 was installed and now he cannot find (has lost) all of his programs and files.
This suggests to me a fresh install / format was done on his main drive, thus giving him win 7 which he now needs drivers for and loosing his data in the process.
If you need the drivers for your HP printer I would suggest checking HP's official website for them which will depend on which country you are in.
A quick google search should bring them up for you.
If you did indeed do a fresh install of win 7 then start digging out your data backups as you will not be getting data back from the drive without specialist software.