Long distance diagnostics is very difficult to do. This is a peer to peer gamers' website, and we don't have anything like the kind of resources that official tech support people have. I have the feeling you have some problem other than the weak GT 620, or your complaint would be about graphics, not crashing, however, we tend to point to those things because there is no support when you have that poor of a video component, anyway.
If you did have a decent setup (and you will almost certainly also need an upgrade to your power supply), Help Center's Official Support techs just might pinpoint the fault quickly enough. It sort of depends on who you've connected to. The quality of personnel is variable.