Looking to Update and Improve Time Management/Life Planning Software created in 2002 L

I'm an individual looking to update/improve and customize an already existing program for personal use. Basically, in 2002 i purchased a time management / life planning software program. this program is now out of print and the company that designed it doesn't make it anymore. however, i loved the functionality of it and certain features it had. the problem was that meant for a Windows 98 and Windows XP environment and the software was never stable even back in 2002. many people complained even back then that anytime u enter too much data into it. it WILL crash for good. and u loose all the data entered into it. and there are other aspects of the program that can be improved on. but i always wished that it had better features added to it. i have all the original foundation executable setup files. but i would like to take the foundation of how the program works and make it more stable and improve the GUI/skin aspect of it and maybe add some small new features that weren't apart of it initially for example. i would love if it had some of the functionality of the 2006 version of Microsoft OneNote with the tab feature to associate