http://support.acer-euro.com/drivers/notebook/as_3620.html, try the Vista drivers. If you know what the model of the graphic chipset is, you can check for Win 7 drivers directly from them per Davcon, but that usually does not work for laptops.
Chances are, you need to go back to XP or use whatever Win7 default runs at. Installing a new OS on a system without checking for compatability is a no-no.