Sonar and Cakewalk Project files

Hello to all CW users; I hope you will be able to help me solve some problems concerning a re-installation of Cakewalk. I have used Cakewalk Pro Suite (version 9) for several years now and I am very satisfied with this application. In my opinion, CWPS9 is much more user friendly than other sequencers that I have tested, including Cubase. I appreciate in particular CWPS9's ability to edit note durations and time management, as the music I am creating requires a rather strict handling of issues such as tempo and rubato. Sadly, my computer clonked out and I had to reformat the hard disk. I have not been able to re-install my program, in fact, I own an old copy of Cakewalk version 4.5 - 5 (yes, I'm conservative in this respect) and I have failed to install either of these 2 versions. After inserting the CDROM's, the installation Wizard does attempt to install these applications, but whenever I try to actually open them the program fails to respond. Therefore, I do not believe the Installation Wizard routine per se is at fault. My computer is an ACER Aspire 8930G with 4 RAM Memory and it is running on Vista. Any help would be very appreciated. I wonder if the new program, Sonar 2, has the capability to read and edit Cakewalk project files in particular, in which case, an upgrade would be considered. Thanks in advance for your attention