i cant run it i dont know why

i downloaded it i logged in and when it was finished it just closed ????????????????????????????????

I'm afraid it's difficult to know what could cause a problem like that but here's a few ideas off the top of my head:

1. Do your computer meet the minimum specifications to run SL?
   
2. Do you have the latest drivers for your video card, sound card, motherboard chipset, etc..
   
3. Are you running a recent version of DirectX?
   

Failing all that, try dropping the support bods an email on support@secondlife.com, and see if they have any ideas.

Post a reply back here if you're not sure where to go looking for drivers or whatever.

Good luck!