Second Life KEEPS ON CRASHING!!! why!!!

I HAVE downloaded Second Life. i have REdownloaded it even,but it KEEPS ON CRASHING! WHY? T.T D:

A good policy to follow when asking for help with a problem with a computer system is to provide information about the system. This description of the system is sometimes called "system specs".

Also good to provide is some information about your situation that might be related to computer use, such as, whether you are in a college dorm or not.

You might want to start with the "Can I Run It?" site at
http://www.systemrequirementslab.com/referrer/srtest

Second Life's systems requirements page:
http://secondlife.com/support/sysreqs.php

What brand and model of computer, if it's a pre-built one that can be thought of as being a brand and model, and if it's not one of those, such as a home built or extensively modified computer, what motherboard?

What operating system?

What processor?

How much RAM memory?

What video card or onboard video processor?

How much video ram?

Wired or wireless network?

What kind of internet service? DSL, cable, dial-up, satellite, or what?

What kind of firewalls, anti-virus, anti-spyware and other security software or hardware measures are in use?

What version of Second Life? (exact version, not the words "the latest version" or other ambiguous time dependent phrase).