> On a Windows server with FB 2.1 I want to try using FB 2.5 for some
> purposes, so I want to do a side by side install of 2.5. The installer
> asks me to stop the existing 2.1 instances, so I suppose it cannot be
> done using the installer?

Download the ZIP archive. Then read the file
install_windows_manually.txt inside.

> So how should I do it? get 2.5 zip package and just unpack it in a
> separate folder? I don't really like to do that under "Program files"...

Basically, yes. You will need to call instsvc.exe, too.

It doesn't have to be Program Files.

Josef