Multiple Domains

-As far as the two IP thing... sure is.
Go into the control panel, and Network Connections, and look at the TCP/IP settings.
You'll be able to multi-home it.
-The easiest way is to create a trust relationship between the two domains. Then you'll be able to jump. Assuming rights are in place.

Here is an article with instructions on assigning additional ip address' to a single nic.
http://support.microsoft.com/default.aspx?scid=http://support.microsoft.com:80/support/kb/articles/Q156/7/72.asp&NoWebContent=1

I don't think you can log into more than one domain. The pc requires a computer account for the domain it belongs to and there isn't any method that I could find to add a second name to it's network id.