Specs listed here, Unidentified Network please help
The problem is the too old and unsupported integrated video, a DirectX 8.1 GPU that is about the equivalent of the old Radeon 9200. You may have had it for 4 years, but it is even older than that. In fact the last driver
update for that chipset from ATI is from early 2006 and only supported up to Windows 2000 at that, Catalystâ„¢ 6.4 Software Component Downloads for Windows 2000 - Motherboard/IGP Drivers
That chipset came out some time in mid to late 2003. Unless the motherboard (Asus P4R8L) came from elsewhere from what I can find it was found in this, http://www.asus.com/product.aspx?P_ID=V3N9NRSB6AxNMlb8
and according to the specs doesn't even have an AGP slot.
This is one of those situations where all things considering you would be better served holding off on Windows 7 until you get a new computer, or live without Aero until then at least.