"If I load the latest via 4 in 1 drivers (which are backward compatible with all via chipsets according to the website) will this upgrade USB to USB2?"
No not if using XP o/system.
"Running XP and if SP1 is not on there I can put it or SP2 on."
You need to have either SP1 or SP2 to have the USB2 drivers, and you might find that even with Via 4 in 1 drivers you will still need a PCI card that does not have a VIA chipset. There has been a known prob with Via chipsets and USB modems for some time, I always try and fit PCI card with a Lucent chipset.