Pentium processors are more ancient than I am. The processor in conjunction with the amount of ram your machine has installed will determine to a great degree what your computer can handle. Check the minimum system requirements for the software you intend to run. If your computer does not have at least the minimum of ANY of the requirements it will usually not open the file, or if it manages to open it then it will probably run erratically, if at all. Windows 7 is a capable platform, but it is not as efficient as 10. Win10 takes a little bit of getting used to it, but it's not different enough to be a nightmare.
At some point in time you will need to upgrade. The applications being produced today are much more sophisticated than what was available even only five years ago. It's either sink or swim. The newer stuff just won't run on old hardware, or old operating systems.