If your package depends on v 2.6, the dependency will usually require v 2.6 or newer.
If you are using Mandriva, urpmi (or the GUI package installer) will resolve any dependencies for you, provided you are installing a Mandriva package. Dependencies are listed in the package you wish to install. Package naming conventions vary from one distribution to another, so if you try to install a RedHat package on a Mandriva system, you may have to resolve any dependencies your self.
Since you mentioned urpmi in your initial question, I take it that you are using Mandriva. If you set up the Internet Software Media Sources for Mandriva (the Mandriva software repositories on the Internet), you will have access to the full range of software packaged for use with it (over 17GB of software for Mandriva Linux 2007.1). These Internet Software Media Sources are mirrored at many ftp servers around the world. The easiest way to set them up is to follow the directions at the Easy URPMI
By using the Mandriva packages and the Mandriva installer, you should not have to deal with package dependencies.
I see questions about software installation frequently, so I have written an article on my blog
that I hope will be of help.