Can you even enter computer 2 from computer 1?
yes, Vista is loaded with security which prevents computers to enter each other without "legally" or manually allowed to do so.
Check list you can work with is:
-Is your computer is the same network group? MSHOME/WORKGROUP
-Can you see or enter each others computers Run/>\computername
-Firewall on or off?
-Accessebility, allow all user to connect to my computer (Somthing like that, should be in your network config.) That is what i meant.