Both computers will need to be in the same group. Right click My Computer > Properties. You should see something titled "Computer name, domain, and workgroup settings" above your Windows product ID. Clicking "Change Settings" under the "Computer name, domain, and workgroup settings" space should allow you to change your PCs name and the Workgroup it's in. Do the same for your Vista. If it asks to reboot, do it.
I share my files the same way as you would (Windows 7 desktop, Vista laptop), and that is all I had to do
Hope it helps/works for you.