Like I already said, the printers are connected directly to the network. Every printer has an IP address, for instance 192.168.5.5
If we need to install this printer on another pc (let's say 192.168.5.101) (because we don't have a print server, I know that would be a lot easier, and hopefully that'll come one day), on xp, i went on my machine to start- run -\\192.168.5.101 and from there we could install the printer, like we were actually on that pc. It wroks from XP to XP, from W7 to XP and from XP to W7, but apparantly there's still a problem between 2 W7 machines.
I also thought that when you had domain admin rights it should work, but I needed to add myself on my machine (W7) on the local admin group to have necessary rights to install a printer on an xp machine. But when I want to do the same on a W7 machine, I'm getting,once again, an error message concerning not having enough rights, even when I'm having domain admin rights and local admin rights on that pc (I tested by adding myself on the local admin group). I still find this strange. I can install printers on other W7 machines by using XP mode on my pc, but it would be easier if I could do this via W7 itself.
Unless someone has another idea, I think we can close this one.