Hi sweetmomo,
The drivers for your HP product are already included in the new Windows 7 operating system! You do not need to download drivers to use the product . Simply connect the printer to your computer with a USB cable, and Windows Update automatically installs the driver for your product. - Source
Please describe the difficulty you are experiencing. I would like to help you get your Deskjet 720c working with your Windows 7 32 bit. What solution did you find for Windows 7 64 bit? The solution for both 32 bit and 64 bit are the same.
When you connect your printer to the computer, Windows 7 detects the hardware and automatically installs the correct driver. A notification lets you know when installation begins and when it is complete.
I look forward to hearing back from you and better understanding the issue you are experiencing.