If Vista runs on this computer then it will be 'flying' Windows 7, however, to be sure to be sure, run the Windows 7 Upgrade Advisor.
Dell doesn't offer any Windows 7 drivers for the Inspiron 1720, so you will have to hunt them down from the part manufacturers' websites (or use the Vista drivers if you can't find any, they should work).
The Stac 92xx C Media HD Audio Vista driver works with Windows 7, depending on your GPU, you will find Windos 7 video drivers at Intel or nVidia, get the latest touchpad driver from Synaptics, the rest should be automatically detected and installed.
Edit: If you find 3 unknown (base) devices after the installation, this is your card reader. grab the Vista driver from the Dell website (the Ricoh driver under "Chipset"), extract it (e.g. with Unversal Extractor) and install the drivers manually via the Device Manager.