There is a team of people that are using filemaker pro 11. The way that they explain it, is the first person that opens the database up, is the host. From there, it looks like others connect and they do their work.
This is not a good way to do this. The database should be hosted from a single machine and that should be the machine where the database files are located. Otherwise, you are dealing with performance penalties and an increased chance of damage to the files themselves.
and when they (w7 machines) are to host, no one can connect to them.
Our system here consists of a mixture of w7 and XP machines. They can all go to Open Remote and succesfully connect to the database with no issues due to the different versions of windows. But we would never ever set this up so that the first user becomes the host.
It sounds like you have your database file located in a shared directory and users are trying to find that shared directory over the network in order to open the database. If so, this is very dangerous as it could seriously corrupt your database file. Once the host computer (as described previously) has used FileMaker Pro or FileMaker Server to open the database, the others should use Open Remote to find the hosting computer and then should select the file to open it.