You should have at least WinXP SP1 installed. I'm not aware of .NET
framework being needed, for USB to work. I don't currently have any
frameworks installed, and my VIA USB2 works.
Check the BIOS, "Onchip USB", and see if it is set
to "V1.1+V2.0".
If you check the USB2 driver on the Foxconn CD, chances are it is
for an older OS. I've seen USB2 drivers, where if you examine them
carefully, they don't do anything when installed on a WinXP system.
(The driver is effectively nulled out.)
The 39MB "chipset drivers" on the Foxconn site, have no USB
portion, so there aren't any USB drivers in there. That leaves
the entry on your CD, as the only potential source, and due to
Microsoft licensing restrictions, Foxconn shouldn't be putting
any USB2 for WinXP on there.
Apparently, if you installed from an SP2 disk, it is possible
for the USB driver to not install. This article suggests you
can attempt to update the driver manually from Device Manager.
I presume you'd be looking for a driver the OS already
knows about.
http://support.microsoft.com/kb/873169/en-us
In the Device Manager, the USB2 entry in the USB section might have
the word "Enhanced" in the name. I can't find any
Device Manager pictures for Nvidia, to confirm what
name Nvidia uses for their USB2 entry. Normally,
there'd be at least one USB entry with the word Enhanced
in the name.