We are currently using CS (mainly Illy & Indesign) at work (yes I know its old), we don't use it too often, but often enough to need it.
Looking at upgrading some of the computers (bigger, faster, sparkling, new etc). Can CS be installed on Win7? Or should I really start seriously considering an Adobe upgrade?
You waited to long for an actually upgrade as I do not think they sell CS 4 and you cannot upgrade to CS
and you are not going to be taking advantage of the native 64 bit CS 5 offers? So unless you can find a unregistered copy of CS 4 upgrade from a retailer before the release date of CS 5 then you will have to buy the ful version.
That out of the way, yes you should upgrade your software with such shiny new equipment and power what would be the point other wise and there are very excellent features in CS5 you might need anyway.
As far as CS running on W7 I think it can with some effort installing it.
backup your entire current installation (older OS with CS)
on your new/upgraded Windows 7 boxes install VirtualBox (free), or Parallels Desktop (paid), or VMware Workstation (paid)
re-install your older OS and CS in a virtual machine.