I have lost the installation disc for my Canon Powershot A40 and the canon website says there isn't a driver for Windows Vista Home Edition. Do you know a solution to this?

Don't give up on your A40 just yet. I still have mine, and although it's only a 2MP camera, IMO the pictures that it can produce in auto mode are some of the best from Canon's line of cameras.
But unfortunately as you've discovered there is no driver for its use with Window's Vista. What this means is that you can't plug the camera directly into your computer to download pictures. But that may be a blessing in disguise as there is an alternative, much easier way, to download photos from digital cameras.
Most professional photographers utilize inexpensive external card readers to download their photos. There are several important reasons discussed in this blog article for using a card reader vice downloading from the camera. USB Card readers are also very inexpensive these day, with cost virtually not an issue. If you do purchase one, make sure that it is stated CF card capable, and for use with Window's Vista.

Use a card reader to download your pictures to a folder you create on your desktop.