My AV detected that some computers in our network are infected with Win32.Sality.Y. Is there any good place I can find the documented details of this virus, so that I can (generally) how the virus works. Then I might be about to find out if it's infected via browser, or email, or USB stick, or other ways.
Where can I find documented details of virus so that I might be able to find out why I am infected?
Google's your best bet. Sality is/was a pretty large botnet, so there's loads of info out there:
You likely got it from a shared drive or an infected USB stick, which is its main propagation method.