You need to compare the game's system requirements to what you actually have..... Saints Row 2 PC Gets System Requirements - Here's what you need to have - Softpedia
It basically looks like your system doesn't meet the game's requirements. And based on what you list as system specs, it looks like you have a lap top, so no, you probably can't update the hardware on it. However, the manufacturer can give you a more definitive answer to hardware upgrades than I can.
As to Windows 7 support, well since the game was released before Windows 7 came out, tech support is using their "get out of jail free" by blaming Windows 7 for the issues you have, even if it's not Windows 7 fault.